Undo System: remove accumulate/store modes

[blender.git] / source / blender / editors / sculpt_paint / paint_image_proj.c

/*
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2001-2002 by NaN Holding BV.
 * All rights reserved.
 *
 * The Original Code is: some of this file.
 */

/** \file blender/editors/sculpt_paint/paint_image_proj.c
 *  \ingroup edsculpt
 *  \brief Functions to paint images in 2D and 3D.
 */

#include <float.h>
#include <string.h>
#include <stdio.h>
#include <math.h>

#include "MEM_guardedalloc.h"

#ifdef WIN32
#  include "BLI_winstuff.h"
#endif

#include "BLI_blenlib.h"
#include "BLI_linklist.h"
#include "BLI_math.h"
#include "BLI_math_bits.h"
#include "BLI_math_color_blend.h"
#include "BLI_memarena.h"
#include "BLI_threads.h"
#include "BLI_utildefines.h"

#include "BLT_translation.h"


#include "IMB_imbuf.h"
#include "IMB_imbuf_types.h"

#include "DNA_brush_types.h"
#include "DNA_material_types.h"
#include "DNA_mesh_types.h"
#include "DNA_meshdata_types.h"
#include "DNA_node_types.h"
#include "DNA_object_types.h"

#include "BKE_brush.h"
#include "BKE_camera.h"
#include "BKE_colorband.h"
#include "BKE_context.h"
#include "BKE_colortools.h"
#include "BKE_idprop.h"
#include "BKE_image.h"
#include "BKE_library.h"
#include "BKE_main.h"
#include "BKE_material.h"
#include "BKE_mesh.h"
#include "BKE_mesh_mapping.h"
#include "BKE_mesh_runtime.h"
#include "BKE_node.h"
#include "BKE_paint.h"
#include "BKE_report.h"
#include "BKE_scene.h"
#include "BKE_screen.h"
#include "BKE_texture.h"

#include "DEG_depsgraph.h"
#include "DEG_depsgraph_query.h"

#include "UI_interface.h"

#include "ED_object.h"
#include "ED_mesh.h"
#include "ED_node.h"
#include "ED_paint.h"
#include "ED_screen.h"
#include "ED_uvedit.h"
#include "ED_view3d.h"

#include "GPU_extensions.h"

#include "WM_api.h"
#include "WM_types.h"

#include "RNA_access.h"
#include "RNA_define.h"
#include "RNA_enum_types.h"

#include "GPU_draw.h"

#include "IMB_colormanagement.h"

#include "bmesh.h"
//#include "bmesh_tools.h"

#include "paint_intern.h"

static void partial_redraw_array_init(ImagePaintPartialRedraw *pr);

/* Defines and Structs */
/* unit_float_to_uchar_clamp as inline function */
BLI_INLINE unsigned char f_to_char(const float val)
{
        return unit_float_to_uchar_clamp(val);
}

/* ProjectionPaint defines */

/* approx the number of buckets to have under the brush,
 * used with the brush size to set the ps->buckets_x and ps->buckets_y value.
 *
 * When 3 - a brush should have ~9 buckets under it at once
 * ...this helps for threading while painting as well as
 * avoiding initializing pixels that wont touch the brush */
#define PROJ_BUCKET_BRUSH_DIV 4

#define PROJ_BUCKET_RECT_MIN 4
#define PROJ_BUCKET_RECT_MAX 256

#define PROJ_BOUNDBOX_DIV 8
#define PROJ_BOUNDBOX_SQUARED  (PROJ_BOUNDBOX_DIV * PROJ_BOUNDBOX_DIV)

//#define PROJ_DEBUG_PAINT 1
//#define PROJ_DEBUG_NOSEAMBLEED 1
//#define PROJ_DEBUG_PRINT_CLIP 1
#define PROJ_DEBUG_WINCLIP 1


#ifndef PROJ_DEBUG_NOSEAMBLEED
/* projectFaceSeamFlags options */
//#define PROJ_FACE_IGNORE      (1<<0)  /* When the face is hidden, backfacing or occluded */
//#define PROJ_FACE_INIT        (1<<1)  /* When we have initialized the faces data */
#define PROJ_FACE_SEAM1 (1 << 0)  /* If this face has a seam on any of its edges */
#define PROJ_FACE_SEAM2 (1 << 1)
#define PROJ_FACE_SEAM3 (1 << 2)

#define PROJ_FACE_NOSEAM1   (1 << 4)
#define PROJ_FACE_NOSEAM2   (1 << 5)
#define PROJ_FACE_NOSEAM3   (1 << 6)

/* face winding */
#define PROJ_FACE_WINDING_INIT 1
#define PROJ_FACE_WINDING_CW 2

/* a slightly scaled down face is used to get fake 3D location for edge pixels in the seams
 * as this number approaches  1.0f the likelihood increases of float precision errors where
 * it is occluded by an adjacent face */
#define PROJ_FACE_SCALE_SEAM    0.99f
#endif  /* PROJ_DEBUG_NOSEAMBLEED */


#define PROJ_SRC_VIEW       1
#define PROJ_SRC_IMAGE_CAM  2
#define PROJ_SRC_IMAGE_VIEW 3
#define PROJ_SRC_VIEW_FILL  4

#define PROJ_VIEW_DATA_ID "view_data"
/* viewmat + winmat + clipsta + clipend + is_ortho */
#define PROJ_VIEW_DATA_SIZE (4 * 4 + 4 * 4 + 3)

#define PROJ_BUCKET_NULL        0
#define PROJ_BUCKET_INIT        (1 << 0)
// #define PROJ_BUCKET_CLONE_INIT       (1<<1)

/* used for testing doubles, if a point is on a line etc */
#define PROJ_GEOM_TOLERANCE 0.00075f
#define PROJ_PIXEL_TOLERANCE 0.01f

/* vert flags */
#define PROJ_VERT_CULL 1

/* to avoid locking in tile initialization */
#define TILE_PENDING POINTER_FROM_INT(-1)

/** This is mainly a convenience struct used so we can keep an array of images we use -
 * their imbufs, etc, in 1 array, When using threads this array is copied for each thread
 * because 'partRedrawRect' and 'touch' values would not be thread safe */
typedef struct ProjPaintImage {
        Image *ima;
        ImBuf *ibuf;
        ImagePaintPartialRedraw *partRedrawRect;
        /** Only used to build undo tiles during painting. */
        volatile void **undoRect;
        /** The mask accumulation must happen on canvas, not on space screen bucket.
         * Here we store the mask rectangle. */
        unsigned short **maskRect;
        /** Store flag to enforce validation of undo rectangle. */
        bool **valid;
        bool touch;
} ProjPaintImage;

/**
 * Handle for stroke (operator customdata)
 */
typedef struct ProjStrokeHandle {
        /* Support for painting from multiple views at once,
         * currently used to implement symmetry painting,
         * we can assume at least the first is set while painting. */
        struct ProjPaintState *ps_views[8];
        int ps_views_tot;
        int symmetry_flags;

        int orig_brush_size;

        bool need_redraw;

        /* trick to bypass regular paint and allow clone picking */
        bool is_clone_cursor_pick;

        /* In ProjPaintState, only here for convenience */
        Scene *scene;
        Brush *brush;
} ProjStrokeHandle;

/* Main projection painting struct passed to all projection painting functions */
typedef struct ProjPaintState {
        View3D *v3d;
        RegionView3D *rv3d;
        ARegion *ar;
        Depsgraph *depsgraph;
        Scene *scene;
        /* PROJ_SRC_**** */
        int source;

        /* the paint color. It can change depending of inverted mode or not */
        float paint_color[3];
        float paint_color_linear[3];
        float dither;

        Brush *brush;
        short tool, blend, mode;

        float brush_size;
        Object *ob;
        /* for symmetry, we need to store modified object matrix */
        float obmat[4][4];
        float obmat_imat[4][4];
        /* end similarities with ImagePaintState */

        Image *stencil_ima;
        Image *canvas_ima;
        Image *clone_ima;
        float stencil_value;

        /* projection painting only */
        /** for multithreading, the first item is sometimes used for non threaded cases too. */
        MemArena *arena_mt[BLENDER_MAX_THREADS];
        /** screen sized 2D array, each pixel has a linked list of ProjPixel's */
        LinkNode **bucketRect;
        /** bucketRect aligned array linkList of faces overlapping each bucket. */
        LinkNode **bucketFaces;
        /** store if the bucks have been initialized. */
        unsigned char *bucketFlags;

        /** store options per vert, now only store if the vert is pointing away from the view. */
        char *vertFlags;
        /** The size of the bucket grid, the grid span's screenMin/screenMax
         * so you can paint outsize the screen or with 2 brushes at once. */
        int buckets_x;
        int buckets_y;

        /** result of project_paint_pixel_sizeof(), constant per stroke. */
        int pixel_sizeof;

        /** size of projectImages array. */
        int image_tot;

        /** verts projected into floating point screen space. */
        float (*screenCoords)[4];
        /** 2D bounds for mesh verts on the screen's plane (screenspace). */
        float screenMin[2];
        float screenMax[2];
        /** Calculated from screenMin & screenMax. */
        float screen_width;
        float screen_height;
        /** from the carea or from the projection render. */
        int winx, winy;

        /* options for projection painting */
        bool  do_layer_clone;
        bool  do_layer_stencil;
        bool  do_layer_stencil_inv;
        bool  do_stencil_brush;
        bool  do_material_slots;

        /** Use raytraced occlusion? - ortherwise will paint right through to the back. */
        bool  do_occlude;
        /** ignore faces with normals pointing away,
         * skips a lot of raycasts if your normals are correctly flipped. */
        bool  do_backfacecull;
        /** mask out pixels based on their normals. */
        bool  do_mask_normal;
        /** mask out pixels based on cavity. */
        bool  do_mask_cavity;
        /** what angle to mask at. */
        float normal_angle;
        /** cos(normal_angle), faster to compare. */
        float normal_angle__cos;
        float normal_angle_inner;
        float normal_angle_inner__cos;
        /** difference between normal_angle and normal_angle_inner, for easy access. */
        float normal_angle_range;

        /** quick access to (me->editflag & ME_EDIT_PAINT_FACE_SEL) */
        bool do_face_sel;
        bool is_ortho;
        /** the object is negative scaled. */
        bool is_flip_object;
        /** use masking during painting. Some operations such as airbrush may disable. */
        bool do_masking;
        /** only to avoid running. */
        bool is_texbrush;
        /** mask brush is applied before masking. */
        bool is_maskbrush;
#ifndef PROJ_DEBUG_NOSEAMBLEED
        float seam_bleed_px;
#endif
        /* clone vars */
        float cloneOffset[2];

        /** Projection matrix, use for getting screen coords. */
        float projectMat[4][4];
        /** inverse of projectMat. */
        float projectMatInv[4][4];
        /** View vector, use for do_backfacecull and for ray casting with an ortho viewport. */
        float viewDir[3];
        /** View location in object relative 3D space, so can compare to verts. */
        float viewPos[3];
        float clipsta, clipend;

        /* reproject vars */
        Image *reproject_image;
        ImBuf *reproject_ibuf;
        bool   reproject_ibuf_free_float;
        bool   reproject_ibuf_free_uchar;

        /* threads */
        int thread_tot;
        int bucketMin[2];
        int bucketMax[2];
        /** must lock threads while accessing these. */
        int context_bucket_x, context_bucket_y;

        struct CurveMapping *cavity_curve;
        BlurKernel *blurkernel;



        /* -------------------------------------------------------------------- */
        /* Vars shared between multiple views (keep last) */
        /**
         * This data is owned by ``ProjStrokeHandle.ps_views[0]``,
         * all other views re-use the data.
         */

#define PROJ_PAINT_STATE_SHARED_MEMCPY(ps_dst, ps_src) \
        MEMCPY_STRUCT_OFS(ps_dst, ps_src, is_shared_user)

#define PROJ_PAINT_STATE_SHARED_CLEAR(ps) \
        MEMSET_STRUCT_OFS(ps, 0, is_shared_user)

        bool is_shared_user;

        ProjPaintImage *projImages;
        /** cavity amount for vertices. */
        float *cavities;

#ifndef PROJ_DEBUG_NOSEAMBLEED
        /** store info about faces, if they are initialized etc*/
        char *faceSeamFlags;
        /** save the winding of the face in uv space,
         * helps as an extra validation step for seam detection. */
        char *faceWindingFlags;
        /** expanded UVs for faces to use as seams. */
        float (*faceSeamUVs)[3][2];
        /** Only needed for when seam_bleed_px is enabled, use to find UV seams. */
        LinkNode **vertFaces;
#endif

        SpinLock *tile_lock;

        Mesh *me_eval;
        bool  me_eval_free;
        int  totlooptri_eval;
        int  totpoly_eval;
        int  totedge_eval;
        int  totvert_eval;

        const MVert    *mvert_eval;
        const MEdge    *medge_eval;
        const MPoly    *mpoly_eval;
        const MLoop    *mloop_eval;
        const MLoopTri *mlooptri_eval;

        const MLoopUV  *mloopuv_stencil_eval;

        /**
         * \note These UV layers are aligned to \a mpoly_eval
         * but each pointer references the start of the layer,
         * so a loop indirection is needed as well.
         */
        const MLoopUV **poly_to_loop_uv;
        /** other UV map, use for cloning between layers. */
        const MLoopUV **poly_to_loop_uv_clone;

        /* Actual material for each index, either from object or Mesh datablock... */
        Material **mat_array;

        bool use_colormanagement;
} ProjPaintState;

typedef union pixelPointer {
        /** float buffer. */
        float *f_pt;
        /** 2 ways to access a char buffer. */
        unsigned int *uint_pt;
        unsigned char *ch_pt;
} PixelPointer;

typedef union pixelStore {
        unsigned char ch[4];
        unsigned int uint;
        float f[4];
} PixelStore;

typedef struct ProjPixel {
        /** the floating point screen projection of this pixel. */
        float projCoSS[2];
        float worldCoSS[3];

        short x_px, y_px;

        /** if anyone wants to paint onto more than 65535 images they can bite me. */
        unsigned short image_index;
        unsigned char bb_cell_index;

        /* for various reasons we may want to mask out painting onto this pixel */
        unsigned short mask;

        /* Only used when the airbrush is disabled.
         * Store the max mask value to avoid painting over an area with a lower opacity
         * with an advantage that we can avoid touching the pixel at all, if the
         * new mask value is lower then mask_accum */
        unsigned short *mask_accum;

        /* horrible hack, store tile valid flag pointer here to re-validate tiles
         * used for anchored and drag-dot strokes */
        bool *valid;

        PixelPointer origColor;
        PixelStore newColor;
        PixelPointer pixel;
} ProjPixel;

typedef struct ProjPixelClone {
        struct ProjPixel __pp;
        PixelStore clonepx;
} ProjPixelClone;

/* undo tile pushing */
typedef struct {
        SpinLock *lock;
        bool masked;
        unsigned short tile_width;
        ImBuf **tmpibuf;
        ProjPaintImage *pjima;
} TileInfo;



/* -------------------------------------------------------------------- */
/** \name MLoopTri accessor functions.
 * \{ */

BLI_INLINE const MPoly *ps_tri_index_to_mpoly(const ProjPaintState *ps, int tri_index)
{
        return &ps->mpoly_eval[ps->mlooptri_eval[tri_index].poly];
}

#define PS_LOOPTRI_AS_VERT_INDEX_3(ps, lt) \
        ps->mloop_eval[lt->tri[0]].v, \
        ps->mloop_eval[lt->tri[1]].v, \
        ps->mloop_eval[lt->tri[2]].v,

#define PS_LOOPTRI_AS_UV_3(uvlayer, lt) \
        uvlayer[lt->poly][lt->tri[0]].uv, \
        uvlayer[lt->poly][lt->tri[1]].uv, \
        uvlayer[lt->poly][lt->tri[2]].uv,

#define PS_LOOPTRI_ASSIGN_UV_3(uv_tri, uvlayer, lt)  { \
        (uv_tri)[0] = uvlayer[lt->poly][lt->tri[0]].uv; \
        (uv_tri)[1] = uvlayer[lt->poly][lt->tri[1]].uv; \
        (uv_tri)[2] = uvlayer[lt->poly][lt->tri[2]].uv; \
} ((void)0)

/** \} */



/* Finish projection painting structs */

static TexPaintSlot *project_paint_face_paint_slot(const ProjPaintState *ps, int tri_index)
{
        const MPoly *mp = ps_tri_index_to_mpoly(ps, tri_index);
        Material *ma = ps->mat_array[mp->mat_nr];
        return ma ? ma->texpaintslot + ma->paint_active_slot : NULL;
}

static Image *project_paint_face_paint_image(const ProjPaintState *ps, int tri_index)
{
        if (ps->do_stencil_brush) {
                return ps->stencil_ima;
        }
        else {
                const MPoly *mp = ps_tri_index_to_mpoly(ps, tri_index);
                Material *ma = ps->mat_array[mp->mat_nr];
                TexPaintSlot *slot = ma ? ma->texpaintslot + ma->paint_active_slot : NULL;
                return slot ? slot->ima : ps->canvas_ima;
        }
}

static TexPaintSlot *project_paint_face_clone_slot(const ProjPaintState *ps, int tri_index)
{
        const MPoly *mp = ps_tri_index_to_mpoly(ps, tri_index);
        Material *ma = ps->mat_array[mp->mat_nr];
        return ma ? ma->texpaintslot + ma->paint_clone_slot : NULL;
}

static Image *project_paint_face_clone_image(const ProjPaintState *ps, int tri_index)
{
        const MPoly *mp = ps_tri_index_to_mpoly(ps, tri_index);
        Material *ma = ps->mat_array[mp->mat_nr];
        TexPaintSlot *slot = ma ? ma->texpaintslot + ma->paint_clone_slot : NULL;
        return slot ? slot->ima : ps->clone_ima;
}

/* fast projection bucket array lookup, use the safe version for bound checking  */
static int project_bucket_offset(const ProjPaintState *ps, const float projCoSS[2])
{
        /* If we were not dealing with screenspace 2D coords we could simple do...
         * ps->bucketRect[x + (y*ps->buckets_y)] */

        /* please explain?
         * projCoSS[0] - ps->screenMin[0]   : zero origin
         * ... / ps->screen_width           : range from 0.0 to 1.0
         * ... * ps->buckets_x              : use as a bucket index
         *
         * Second multiplication does similar but for vertical offset
         */
        return ( (int)(((projCoSS[0] - ps->screenMin[0]) / ps->screen_width)  * ps->buckets_x)) +
               (((int)(((projCoSS[1] - ps->screenMin[1]) / ps->screen_height) * ps->buckets_y)) * ps->buckets_x);
}

static int project_bucket_offset_safe(const ProjPaintState *ps, const float projCoSS[2])
{
        int bucket_index = project_bucket_offset(ps, projCoSS);

        if (bucket_index < 0 || bucket_index >= ps->buckets_x * ps->buckets_y) {
                return -1;
        }
        else {
                return bucket_index;
        }
}

static float VecZDepthOrtho(
        const float pt[2],
        const float v1[3], const float v2[3], const float v3[3],
        float w[3])
{
        barycentric_weights_v2(v1, v2, v3, pt, w);
        return (v1[2] * w[0]) + (v2[2] * w[1]) + (v3[2] * w[2]);
}

static float VecZDepthPersp(
        const float pt[2],
        const float v1[4], const float v2[4], const float v3[4],
        float w[3])
{
        float wtot_inv, wtot;
        float w_tmp[3];

        barycentric_weights_v2_persp(v1, v2, v3, pt, w);
        /* for the depth we need the weights to match what
         * barycentric_weights_v2 would return, in this case its easiest just to
         * undo the 4th axis division and make it unit-sum
         *
         * don't call barycentric_weights_v2() because our callers expect 'w'
         * to be weighted from the perspective */
        w_tmp[0] = w[0] * v1[3];
        w_tmp[1] = w[1] * v2[3];
        w_tmp[2] = w[2] * v3[3];

        wtot = w_tmp[0] + w_tmp[1] + w_tmp[2];

        if (wtot != 0.0f) {
                wtot_inv = 1.0f / wtot;

                w_tmp[0] = w_tmp[0] * wtot_inv;
                w_tmp[1] = w_tmp[1] * wtot_inv;
                w_tmp[2] = w_tmp[2] * wtot_inv;
        }
        else /* dummy values for zero area face */
                w_tmp[0] = w_tmp[1] = w_tmp[2] = 1.0f / 3.0f;
        /* done mimicking barycentric_weights_v2() */

        return (v1[2] * w_tmp[0]) + (v2[2] * w_tmp[1]) + (v3[2] * w_tmp[2]);
}


/* Return the top-most face index that the screen space coord 'pt' touches (or -1) */
static int project_paint_PickFace(
        const ProjPaintState *ps, const float pt[2],
        float w[3])
{
        LinkNode *node;
        float w_tmp[3];
        int bucket_index;
        int best_tri_index = -1;
        float z_depth_best = FLT_MAX, z_depth;

        bucket_index = project_bucket_offset_safe(ps, pt);
        if (bucket_index == -1)
                return -1;



        /* we could return 0 for 1 face buckets, as long as this function assumes
         * that the point its testing is only every originated from an existing face */

        for (node = ps->bucketFaces[bucket_index]; node; node = node->next) {
                const int tri_index = POINTER_AS_INT(node->link);
                const MLoopTri *lt = &ps->mlooptri_eval[tri_index];
                const float *vtri_ss[3] = {
                    ps->screenCoords[ps->mloop_eval[lt->tri[0]].v],
                    ps->screenCoords[ps->mloop_eval[lt->tri[1]].v],
                    ps->screenCoords[ps->mloop_eval[lt->tri[2]].v],
                };


                if (isect_point_tri_v2(pt, UNPACK3(vtri_ss))) {
                        if (ps->is_ortho) {
                                z_depth = VecZDepthOrtho(pt, UNPACK3(vtri_ss), w_tmp);
                        }
                        else {
                                z_depth = VecZDepthPersp(pt, UNPACK3(vtri_ss), w_tmp);
                        }

                        if (z_depth < z_depth_best) {
                                best_tri_index = tri_index;
                                z_depth_best = z_depth;
                                copy_v3_v3(w, w_tmp);
                        }
                }
        }

        /** will be -1 or a valid face. */
        return best_tri_index;
}

/* Converts a uv coord into a pixel location wrapping if the uv is outside 0-1 range */
static void uvco_to_wrapped_pxco(const float uv[2], int ibuf_x, int ibuf_y, float *x, float *y)
{
        /* use */
        *x = fmodf(uv[0], 1.0f);
        *y = fmodf(uv[1], 1.0f);

        if (*x < 0.0f) *x += 1.0f;
        if (*y < 0.0f) *y += 1.0f;

        *x = *x * ibuf_x - 0.5f;
        *y = *y * ibuf_y - 0.5f;
}

/* Set the top-most face color that the screen space coord 'pt' touches
 * (or return 0 if none touch) */
static bool project_paint_PickColor(
        const ProjPaintState *ps, const float pt[2],
        float *rgba_fp, unsigned char *rgba, const bool interp)
{
        const MLoopTri *lt;
        const float *lt_tri_uv[3];
        float w[3], uv[2];
        int tri_index;
        Image *ima;
        ImBuf *ibuf;
        int xi, yi;

        tri_index = project_paint_PickFace(ps, pt, w);

        if (tri_index == -1)
                return 0;

        lt = &ps->mlooptri_eval[tri_index];
        PS_LOOPTRI_ASSIGN_UV_3(lt_tri_uv, ps->poly_to_loop_uv, lt);

        interp_v2_v2v2v2(uv, UNPACK3(lt_tri_uv), w);

        ima = project_paint_face_paint_image(ps, tri_index);
        /** we must have got the imbuf before getting here. */
        ibuf = BKE_image_get_first_ibuf(ima);
        if (!ibuf) return 0;

        if (interp) {
                float x, y;
                uvco_to_wrapped_pxco(uv, ibuf->x, ibuf->y, &x, &y);

                if (ibuf->rect_float) {
                        if (rgba_fp) {
                                bilinear_interpolation_color_wrap(ibuf, NULL, rgba_fp, x, y);
                        }
                        else {
                                float rgba_tmp_f[4];
                                bilinear_interpolation_color_wrap(ibuf, NULL, rgba_tmp_f, x, y);
                                premul_float_to_straight_uchar(rgba, rgba_tmp_f);
                        }
                }
                else {
                        if (rgba) {
                                bilinear_interpolation_color_wrap(ibuf, rgba, NULL, x, y);
                        }
                        else {
                                unsigned char rgba_tmp[4];
                                bilinear_interpolation_color_wrap(ibuf, rgba_tmp, NULL, x, y);
                                straight_uchar_to_premul_float(rgba_fp, rgba_tmp);
                        }
                }
        }
        else {
                //xi = (int)((uv[0]*ibuf->x) + 0.5f);
                //yi = (int)((uv[1]*ibuf->y) + 0.5f);
                //if (xi < 0 || xi >= ibuf->x  ||  yi < 0 || yi >= ibuf->y) return 0;

                /* wrap */
                xi = mod_i((int)(uv[0] * ibuf->x), ibuf->x);
                yi = mod_i((int)(uv[1] * ibuf->y), ibuf->y);

                if (rgba) {
                        if (ibuf->rect_float) {
                                const float *rgba_tmp_fp = ibuf->rect_float + (xi + yi * ibuf->x * 4);
                                premul_float_to_straight_uchar(rgba, rgba_tmp_fp);
                        }
                        else {
                                *((unsigned int *)rgba) = *(unsigned int *)(((char *)ibuf->rect) + ((xi + yi * ibuf->x) * 4));
                        }
                }

                if (rgba_fp) {
                        if (ibuf->rect_float) {
                                copy_v4_v4(rgba_fp, (ibuf->rect_float + ((xi + yi * ibuf->x) * 4)));
                        }
                        else {
                                unsigned char *tmp_ch = ((unsigned char *)ibuf->rect) + ((xi + yi * ibuf->x) * 4);
                                straight_uchar_to_premul_float(rgba_fp, tmp_ch);
                        }
                }
        }
        BKE_image_release_ibuf(ima, ibuf, NULL);
        return 1;
}

/**
 * Check if 'pt' is infront of the 3 verts on the Z axis (used for screenspace occlusion test)
 * \return
 * -  `0`:   no occlusion
 * - `-1`: no occlusion but 2D intersection is true
 * -  `1`: occluded
 * -  `2`: occluded with `w[3]` weights set (need to know in some cases)
 */
static int project_paint_occlude_ptv(
        const float pt[3],
        const float v1[4], const float v2[4], const float v3[4],
        float w[3], const bool is_ortho)
{
        /* if all are behind us, return false */
        if (v1[2] > pt[2] && v2[2] > pt[2] && v3[2] > pt[2])
                return 0;

        /* do a 2D point in try intersection */
        if (!isect_point_tri_v2(pt, v1, v2, v3))
                return 0;


        /* From here on we know there IS an intersection */
        /* if ALL of the verts are infront of us then we know it intersects ? */
        if (v1[2] < pt[2] && v2[2] < pt[2] && v3[2] < pt[2]) {
                return 1;
        }
        else {
                /* we intersect? - find the exact depth at the point of intersection */
                /* Is this point is occluded by another face? */
                if (is_ortho) {
                        if (VecZDepthOrtho(pt, v1, v2, v3, w) < pt[2]) return 2;
                }
                else {
                        if (VecZDepthPersp(pt, v1, v2, v3, w) < pt[2]) return 2;
                }
        }
        return -1;
}


static int project_paint_occlude_ptv_clip(
        const float pt[3],
        const float v1[4], const float v2[4], const float v3[4],
        const float v1_3d[3], const float v2_3d[3], const float v3_3d[3],
        float w[3], const bool is_ortho, RegionView3D *rv3d)
{
        float wco[3];
        int ret = project_paint_occlude_ptv(pt, v1, v2, v3, w, is_ortho);

        if (ret <= 0)
                return ret;

        if (ret == 1) { /* weights not calculated */
                if (is_ortho) {
                        barycentric_weights_v2(v1, v2, v3, pt, w);
                }
                else {
                        barycentric_weights_v2_persp(v1, v2, v3, pt, w);
                }
        }

        /* Test if we're in the clipped area, */
        interp_v3_v3v3v3(wco, v1_3d, v2_3d, v3_3d, w);

        if (!ED_view3d_clipping_test(rv3d, wco, true)) {
                return 1;
        }

        return -1;
}


/* Check if a screenspace location is occluded by any other faces
 * check, pixelScreenCo must be in screenspace, its Z-Depth only needs to be used for comparison
 * and doesn't need to be correct in relation to X and Y coords
 * (this is the case in perspective view) */
static bool project_bucket_point_occluded(
        const ProjPaintState *ps, LinkNode *bucketFace,
        const int orig_face, const float pixelScreenCo[4])
{
        int isect_ret;
        const bool do_clip = ps->rv3d ? (ps->rv3d->rflag & RV3D_CLIPPING) != 0 : 0;

        /* we could return 0 for 1 face buckets, as long as this function assumes
         * that the point its testing is only every originated from an existing face */

        for (; bucketFace; bucketFace = bucketFace->next) {
                const int tri_index = POINTER_AS_INT(bucketFace->link);

                if (orig_face != tri_index) {
                        const MLoopTri *lt = &ps->mlooptri_eval[tri_index];
                        const float *vtri_ss[3] = {
                            ps->screenCoords[ps->mloop_eval[lt->tri[0]].v],
                            ps->screenCoords[ps->mloop_eval[lt->tri[1]].v],
                            ps->screenCoords[ps->mloop_eval[lt->tri[2]].v],
                        };
                        float w[3];

                        if (do_clip) {
                                const float *vtri_co[3] = {
                                    ps->mvert_eval[ps->mloop_eval[lt->tri[0]].v].co,
                                    ps->mvert_eval[ps->mloop_eval[lt->tri[1]].v].co,
                                    ps->mvert_eval[ps->mloop_eval[lt->tri[2]].v].co,
                                };
                                isect_ret = project_paint_occlude_ptv_clip(
                                        pixelScreenCo, UNPACK3(vtri_ss), UNPACK3(vtri_co),
                                        w, ps->is_ortho, ps->rv3d);
                        }
                        else {
                                isect_ret = project_paint_occlude_ptv(
                                        pixelScreenCo, UNPACK3(vtri_ss),
                                        w, ps->is_ortho);
                        }

                        if (isect_ret >= 1) {
                                /* TODO - we may want to cache the first hit,
                                 * it is not possible to swap the face order in the list anymore */
                                return true;
                        }
                }
        }
        return false;
}

/* basic line intersection, could move to math_geom.c, 2 points with a horiz line
 * 1 for an intersection, 2 if the first point is aligned, 3 if the second point is aligned */
#define ISECT_TRUE 1
#define ISECT_TRUE_P1 2
#define ISECT_TRUE_P2 3
static int line_isect_y(const float p1[2], const float p2[2], const float y_level, float *x_isect)
{
        float y_diff;

        /* are we touching the first point? - no interpolation needed */
        if (y_level == p1[1]) {
                *x_isect = p1[0];
                return ISECT_TRUE_P1;
        }
        /* are we touching the second point? - no interpolation needed */
        if (y_level == p2[1]) {
                *x_isect = p2[0];
                return ISECT_TRUE_P2;
        }

        /** yuck, horizontal line, we cant do much here. */
        y_diff = fabsf(p1[1] - p2[1]);

        if (y_diff < 0.000001f) {
                *x_isect = (p1[0] + p2[0]) * 0.5f;
                return ISECT_TRUE;
        }

        if (p1[1] > y_level && p2[1] < y_level) {
                /* (p1[1] - p2[1]); */
                *x_isect = (p2[0] * (p1[1] - y_level) + p1[0] * (y_level - p2[1])) / y_diff;
                return ISECT_TRUE;
        }
        else if (p1[1] < y_level && p2[1] > y_level) {
                /* (p2[1] - p1[1]); */
                *x_isect = (p2[0] * (y_level - p1[1]) + p1[0] * (p2[1] - y_level)) / y_diff;
                return ISECT_TRUE;
        }
        else {
                return 0;
        }
}

static int line_isect_x(const float p1[2], const float p2[2], const float x_level, float *y_isect)
{
        float x_diff;

        if (x_level == p1[0]) { /* are we touching the first point? - no interpolation needed */
                *y_isect = p1[1];
                return ISECT_TRUE_P1;
        }
        if (x_level == p2[0]) { /* are we touching the second point? - no interpolation needed */
                *y_isect = p2[1];
                return ISECT_TRUE_P2;
        }

        /* yuck, horizontal line, we cant do much here */
        x_diff = fabsf(p1[0] - p2[0]);

        /* yuck, vertical line, we cant do much here */
        if (x_diff < 0.000001f) {
                *y_isect = (p1[0] + p2[0]) * 0.5f;
                return ISECT_TRUE;
        }

        if (p1[0] > x_level && p2[0] < x_level) {
                /* (p1[0] - p2[0]); */
                *y_isect = (p2[1] * (p1[0] - x_level) + p1[1] * (x_level - p2[0])) / x_diff;
                return ISECT_TRUE;
        }
        else if (p1[0] < x_level && p2[0] > x_level) {
                /* (p2[0] - p1[0]); */
                *y_isect = (p2[1] * (x_level - p1[0]) + p1[1] * (p2[0] - x_level)) / x_diff;
                return ISECT_TRUE;
        }
        else {
                return 0;
        }
}

/* simple func use for comparing UV locations to check if there are seams.
 * Its possible this gives incorrect results, when the UVs for 1 face go into the next
 * tile, but do not do this for the adjacent face, it could return a false positive.
 * This is so unlikely that Id not worry about it. */
#ifndef PROJ_DEBUG_NOSEAMBLEED
static bool cmp_uv(const float vec2a[2], const float vec2b[2])
{
        /* if the UV's are not between 0.0 and 1.0 */
        float xa = fmodf(vec2a[0], 1.0f);
        float ya = fmodf(vec2a[1], 1.0f);

        float xb = fmodf(vec2b[0], 1.0f);
        float yb = fmodf(vec2b[1], 1.0f);

        if (xa < 0.0f) xa += 1.0f;
        if (ya < 0.0f) ya += 1.0f;

        if (xb < 0.0f) xb += 1.0f;
        if (yb < 0.0f) yb += 1.0f;

        return ((fabsf(xa - xb) < PROJ_GEOM_TOLERANCE) && (fabsf(ya - yb) < PROJ_GEOM_TOLERANCE)) ? 1 : 0;
}
#endif

/* set min_px and max_px to the image space bounds of the UV coords
 * return zero if there is no area in the returned rectangle */
#ifndef PROJ_DEBUG_NOSEAMBLEED
static bool pixel_bounds_uv(
        const float uv_quad[4][2],
        rcti *bounds_px,
        const int ibuf_x, const int ibuf_y
        )
{
        /* UV bounds */
        float min_uv[2], max_uv[2];

        INIT_MINMAX2(min_uv, max_uv);

        minmax_v2v2_v2(min_uv, max_uv, uv_quad[0]);
        minmax_v2v2_v2(min_uv, max_uv, uv_quad[1]);
        minmax_v2v2_v2(min_uv, max_uv, uv_quad[2]);
        minmax_v2v2_v2(min_uv, max_uv, uv_quad[3]);

        bounds_px->xmin = (int)(ibuf_x * min_uv[0]);
        bounds_px->ymin = (int)(ibuf_y * min_uv[1]);

        bounds_px->xmax = (int)(ibuf_x * max_uv[0]) + 1;
        bounds_px->ymax = (int)(ibuf_y * max_uv[1]) + 1;

        /*printf("%d %d %d %d\n", min_px[0], min_px[1], max_px[0], max_px[1]);*/

        /* face uses no UV area when quantized to pixels? */
        return (bounds_px->xmin == bounds_px->xmax || bounds_px->ymin == bounds_px->ymax) ? 0 : 1;
}
#endif

static bool pixel_bounds_array(float (*uv)[2], rcti *bounds_px, const int ibuf_x, const int ibuf_y, int tot)
{
        /* UV bounds */
        float min_uv[2], max_uv[2];

        if (tot == 0) {
                return 0;
        }

        INIT_MINMAX2(min_uv, max_uv);

        while (tot--) {
                minmax_v2v2_v2(min_uv, max_uv, (*uv));
                uv++;
        }

        bounds_px->xmin = (int)(ibuf_x * min_uv[0]);
        bounds_px->ymin = (int)(ibuf_y * min_uv[1]);

        bounds_px->xmax = (int)(ibuf_x * max_uv[0]) + 1;
        bounds_px->ymax = (int)(ibuf_y * max_uv[1]) + 1;

        /*printf("%d %d %d %d\n", min_px[0], min_px[1], max_px[0], max_px[1]);*/

        /* face uses no UV area when quantized to pixels? */
        return (bounds_px->xmin == bounds_px->xmax || bounds_px->ymin == bounds_px->ymax) ? 0 : 1;
}

#ifndef PROJ_DEBUG_NOSEAMBLEED

static void project_face_winding_init(const ProjPaintState *ps, const int tri_index)
{
        /* detect the winding of faces in uv space */
        const MLoopTri *lt = &ps->mlooptri_eval[tri_index];
        const float *lt_tri_uv[3] = { PS_LOOPTRI_AS_UV_3(ps->poly_to_loop_uv, lt) };
        float winding = cross_tri_v2(lt_tri_uv[0], lt_tri_uv[1], lt_tri_uv[2]);

        if (winding > 0)
                ps->faceWindingFlags[tri_index] |= PROJ_FACE_WINDING_CW;

        ps->faceWindingFlags[tri_index] |= PROJ_FACE_WINDING_INIT;
}

/* This function returns 1 if this face has a seam along the 2 face-vert indices
 * 'orig_i1_fidx' and 'orig_i2_fidx' */
static bool check_seam(
        const ProjPaintState *ps,
        const int orig_face, const int orig_i1_fidx, const int orig_i2_fidx,
        int *other_face, int *orig_fidx)
{
        const MLoopTri *orig_lt = &ps->mlooptri_eval[orig_face];
        const float *orig_lt_tri_uv[3] = { PS_LOOPTRI_AS_UV_3(ps->poly_to_loop_uv, orig_lt) };
        /* vert indices from face vert order indices */
        const unsigned int i1 = ps->mloop_eval[orig_lt->tri[orig_i1_fidx]].v;
        const unsigned int i2 = ps->mloop_eval[orig_lt->tri[orig_i2_fidx]].v;
        LinkNode *node;
        /* index in face */
        int i1_fidx = -1, i2_fidx = -1;

        for (node = ps->vertFaces[i1]; node; node = node->next) {
                const int tri_index = POINTER_AS_INT(node->link);

                if (tri_index != orig_face) {
                        const MLoopTri *lt = &ps->mlooptri_eval[tri_index];
                        const int lt_vtri[3] = { PS_LOOPTRI_AS_VERT_INDEX_3(ps, lt) };
                        /* could check if the 2 faces images match here,
                         * but then there wouldn't be a way to return the opposite face's info */


                        /* We need to know the order of the verts in the adjacent face
                         * set the i1_fidx and i2_fidx to (0,1,2,3) */
                        i1_fidx = BKE_MESH_TESSTRI_VINDEX_ORDER(lt_vtri, i1);
                        i2_fidx = BKE_MESH_TESSTRI_VINDEX_ORDER(lt_vtri, i2);

                        /* Only need to check if 'i2_fidx' is valid because we know i1_fidx is the same vert on both faces */
                        if (i2_fidx != -1) {
                                const float *lt_tri_uv[3] = { PS_LOOPTRI_AS_UV_3(ps->poly_to_loop_uv, lt) };
                                Image *tpage = project_paint_face_paint_image(ps, tri_index);
                                Image *orig_tpage = project_paint_face_paint_image(ps, orig_face);

                                BLI_assert(i1_fidx != -1);

                                /* This IS an adjacent face!, now lets check if the UVs are ok */

                                /* set up the other face */
                                *other_face = tri_index;

                                /* we check if difference is 1 here, else we might have a case of edge 2-0 for a tri */
                                *orig_fidx = (i1_fidx < i2_fidx && (i2_fidx - i1_fidx == 1)) ? i1_fidx : i2_fidx;

                                /* initialize face winding if needed */
                                if ((ps->faceWindingFlags[tri_index] & PROJ_FACE_WINDING_INIT) == 0)
                                        project_face_winding_init(ps, tri_index);

                                /* first test if they have the same image */
                                if ((orig_tpage == tpage) &&
                                    cmp_uv(orig_lt_tri_uv[orig_i1_fidx], lt_tri_uv[i1_fidx]) &&
                                    cmp_uv(orig_lt_tri_uv[orig_i2_fidx], lt_tri_uv[i2_fidx]))
                                {
                                        /* if faces don't have the same winding in uv space,
                                         * they are on the same side so edge is boundary */
                                        if ((ps->faceWindingFlags[tri_index] & PROJ_FACE_WINDING_CW) !=
                                            (ps->faceWindingFlags[orig_face] & PROJ_FACE_WINDING_CW))
                                        {
                                                return 1;
                                        }

                                        // printf("SEAM (NONE)\n");
                                        return 0;

                                }
                                else {
                                        // printf("SEAM (UV GAP)\n");
                                        return 1;
                                }
                        }
                }
        }
        // printf("SEAM (NO FACE)\n");
        *other_face = -1;
        return 1;
}

#define SMALL_NUMBER  1.e-6f
BLI_INLINE float shell_v2v2_normal_dir_to_dist(float n[2], float d[2])
{
        const float angle_cos = (normalize_v2(n) < SMALL_NUMBER) ? fabsf(dot_v2v2(d, n)) : 0.0f;
        return (UNLIKELY(angle_cos < SMALL_NUMBER)) ? 1.0f : (1.0f / angle_cos);
}
#undef SMALL_NUMBER

/* Calculate outset UV's, this is not the same as simply scaling the UVs,
 * since the outset coords are a margin that keep an even distance from the original UV's,
 * note that the image aspect is taken into account */
static void uv_image_outset(
        float (*orig_uv)[2], float (*outset_uv)[2], const float scaler,
        const int ibuf_x, const int ibuf_y, const bool cw)
{
        /* disallow shell-thickness to outset extreme values,
         * otherwise near zero area UV's may extend thousands of pixels. */
        const float scale_clamp = 5.0f;

        float a1, a2, a3;
        /* pixelspace uv's */
        float puv[3][2];
        /* normals */
        float no1[2], no2[2], no3[2];
        float dir1[2], dir2[2], dir3[2];
        float ibuf_inv[2];

        ibuf_inv[0] = 1.0f / (float)ibuf_x;
        ibuf_inv[1] = 1.0f / (float)ibuf_y;

        /* make UV's in pixel space so we can */
        puv[0][0] = orig_uv[0][0] * ibuf_x;
        puv[0][1] = orig_uv[0][1] * ibuf_y;

        puv[1][0] = orig_uv[1][0] * ibuf_x;
        puv[1][1] = orig_uv[1][1] * ibuf_y;

        puv[2][0] = orig_uv[2][0] * ibuf_x;
        puv[2][1] = orig_uv[2][1] * ibuf_y;

        /* face edge directions */
        sub_v2_v2v2(dir1, puv[1], puv[0]);
        sub_v2_v2v2(dir2, puv[2], puv[1]);
        sub_v2_v2v2(dir3, puv[0], puv[2]);
        normalize_v2(dir1);
        normalize_v2(dir2);
        normalize_v2(dir3);

        /* here we just use the orthonormality property (a1, a2) dot (a2, -a1) = 0
         * to get normals from the edge directions based on the winding */
        if (cw) {
                no1[0] = -dir3[1] - dir1[1];
                no1[1] =  dir3[0] + dir1[0];
                no2[0] = -dir1[1] - dir2[1];
                no2[1] =  dir1[0] + dir2[0];
                no3[0] = -dir2[1] - dir3[1];
                no3[1] =  dir2[0] + dir3[0];
        }
        else {
                no1[0] =  dir3[1] + dir1[1];
                no1[1] = -dir3[0] - dir1[0];
                no2[0] =  dir1[1] + dir2[1];
                no2[1] = -dir1[0] - dir2[0];
                no3[0] =  dir2[1] + dir3[1];
                no3[1] = -dir2[0] - dir3[0];
        }

        a1 = shell_v2v2_normal_dir_to_dist(no1, dir3);
        a2 = shell_v2v2_normal_dir_to_dist(no2, dir1);
        a3 = shell_v2v2_normal_dir_to_dist(no3, dir2);

        CLAMP_MAX(a1, scale_clamp);
        CLAMP_MAX(a2, scale_clamp);
        CLAMP_MAX(a3, scale_clamp);

        mul_v2_fl(no1, a1 * scaler);
        mul_v2_fl(no2, a2 * scaler);
        mul_v2_fl(no3, a3 * scaler);
        add_v2_v2v2(outset_uv[0], puv[0], no1);
        add_v2_v2v2(outset_uv[1], puv[1], no2);
        add_v2_v2v2(outset_uv[2], puv[2], no3);

        mul_v2_v2(outset_uv[0], ibuf_inv);
        mul_v2_v2(outset_uv[1], ibuf_inv);
        mul_v2_v2(outset_uv[2], ibuf_inv);
}

/*
 * Be tricky with flags, first 4 bits are PROJ_FACE_SEAM1 to 4, last 4 bits are PROJ_FACE_NOSEAM1 to 4
 * 1<<i - where i is (0-3)
 *
 * If we're multithreadng, make sure threads are locked when this is called
 */
static void project_face_seams_init(const ProjPaintState *ps, const int tri_index)
{
        /* vars for the other face, we also set its flag */
        int other_face, other_fidx;
        int fidx1 = 2;
        /* next fidx in the face (0,1,2,3) -> (1,2,3,0) or (0,1,2) -> (1,2,0) for a tri */
        int fidx2 = 0;

        /* initialize face winding if needed */
        if ((ps->faceWindingFlags[tri_index] & PROJ_FACE_WINDING_INIT) == 0)
                project_face_winding_init(ps, tri_index);

        do {
                if ((ps->faceSeamFlags[tri_index] & (1 << fidx1 | 16 << fidx1)) == 0) {
                        if (check_seam(ps, tri_index, fidx1, fidx2, &other_face, &other_fidx)) {
                                ps->faceSeamFlags[tri_index] |= 1 << fidx1;
                                if (other_face != -1)
                                        ps->faceSeamFlags[other_face] |= 1 << other_fidx;
                        }
                        else {
                                ps->faceSeamFlags[tri_index] |= 16 << fidx1;
                                if (other_face != -1) {
                                        /* second 4 bits for disabled */
                                        ps->faceSeamFlags[other_face] |= 16 << other_fidx;
                                }
                        }
                }

                fidx2 = fidx1;
        } while (fidx1--);
}
#endif // PROJ_DEBUG_NOSEAMBLEED


/* Converts a UV location to a 3D screenspace location
 * Takes a 'uv' and 3 UV coords, and sets the values of pixelScreenCo
 *
 * This is used for finding a pixels location in screenspace for painting */
static void screen_px_from_ortho(
        const float uv[2],
        const float v1co[3], const float v2co[3], const float v3co[3],  /* Screenspace coords */
        const float uv1co[2], const float uv2co[2], const float uv3co[2],
        float pixelScreenCo[4],
        float w[3])
{
        barycentric_weights_v2(uv1co, uv2co, uv3co, uv, w);
        interp_v3_v3v3v3(pixelScreenCo, v1co, v2co, v3co, w);
}

/* same as screen_px_from_ortho except we
 * do perspective correction on the pixel coordinate */
static void screen_px_from_persp(
        const float uv[2],
        const float v1co[4], const float v2co[4], const float v3co[4],  /* screenspace coords */
        const float uv1co[2], const float uv2co[2], const float uv3co[2],
        float pixelScreenCo[4],
        float w[3])
{
        float w_int[3];
        float wtot_inv, wtot;
        barycentric_weights_v2(uv1co, uv2co, uv3co, uv, w);

        /* re-weight from the 4th coord of each screen vert */
        w_int[0] = w[0] * v1co[3];
        w_int[1] = w[1] * v2co[3];
        w_int[2] = w[2] * v3co[3];

        wtot = w_int[0] + w_int[1] + w_int[2];

        if (wtot > 0.0f) {
                wtot_inv = 1.0f / wtot;
                w_int[0] *= wtot_inv;
                w_int[1] *= wtot_inv;
                w_int[2] *= wtot_inv;
        }
        else {
                w[0] = w[1] = w[2] =
                /* dummy values for zero area face */
                w_int[0] = w_int[1] = w_int[2] = 1.0f / 3.0f;
        }
        /* done re-weighting */

        /* do interpolation based on projected weight */
        interp_v3_v3v3v3(pixelScreenCo, v1co, v2co, v3co, w_int);
}


/**
 * Set a direction vector based on a screen location.
 * (use for perspective view, else we can simply use `ps->viewDir`)
 *
 * Similar functionality to #ED_view3d_win_to_vector
 *
 * \param r_dir: Resulting direction (length is undefined).
 */
static void screen_px_to_vector_persp(
        int winx, int winy, const float projmat_inv[4][4], const float view_pos[3],
        const float co_px[2],
        float r_dir[3])
{
        r_dir[0] = 2.0f * (co_px[0] / winx) - 1.0f;
        r_dir[1] = 2.0f * (co_px[1] / winy) - 1.0f;
        r_dir[2] = -0.5f;
        mul_project_m4_v3((float(*)[4])projmat_inv, r_dir);
        sub_v3_v3(r_dir, view_pos);
}

/**
 * Special function to return the factor to a point along a line in pixel space.
 *
 * This is needed since we can't use #line_point_factor_v2 for perspective screen-space coords.
 *
 * \param p: 2D screen-space location.
 * \param v1, v2: 3D object-space locations.
 */
static float screen_px_line_point_factor_v2_persp(
        const ProjPaintState *ps,
        const float p[2],
        const float v1[3], const float v2[3])
{
        const float zero[3] = {0};
        float v1_proj[3], v2_proj[3];
        float dir[3];

        screen_px_to_vector_persp(ps->winx, ps->winy, ps->projectMatInv, ps->viewPos, p, dir);

        sub_v3_v3v3(v1_proj, v1, ps->viewPos);
        sub_v3_v3v3(v2_proj, v2, ps->viewPos);

        project_plane_v3_v3v3(v1_proj, v1_proj, dir);
        project_plane_v3_v3v3(v2_proj, v2_proj, dir);

        return line_point_factor_v2(zero, v1_proj, v2_proj);
}


static void project_face_pixel(
        const float *lt_tri_uv[3], ImBuf *ibuf_other, const float w[3],
        unsigned char rgba_ub[4], float rgba_f[4])
{
        float uv_other[2], x, y;

        interp_v2_v2v2v2(uv_other, UNPACK3(lt_tri_uv), w);

        /* use */
        uvco_to_wrapped_pxco(uv_other, ibuf_other->x, ibuf_other->y, &x, &y);

        if (ibuf_other->rect_float) { /* from float to float */
                bilinear_interpolation_color_wrap(ibuf_other, NULL, rgba_f, x, y);
        }
        else { /* from char to float */
                bilinear_interpolation_color_wrap(ibuf_other, rgba_ub, NULL, x, y);
        }

}

/* run this outside project_paint_uvpixel_init since pixels with mask 0 don't need init */
static float project_paint_uvpixel_mask(
        const ProjPaintState *ps,
        const int tri_index,
        const float w[3])
{
        float mask;

        /* Image Mask */
        if (ps->do_layer_stencil) {
                /* another UV maps image is masking this one's */
                ImBuf *ibuf_other;
                Image *other_tpage = ps->stencil_ima;

                if (other_tpage && (ibuf_other = BKE_image_acquire_ibuf(other_tpage, NULL, NULL))) {
                        const MLoopTri *lt_other = &ps->mlooptri_eval[tri_index];
                        const float *lt_other_tri_uv[3] = { PS_LOOPTRI_AS_UV_3(ps->poly_to_loop_uv, lt_other) };

                        /* BKE_image_acquire_ibuf - TODO - this may be slow */
                        unsigned char rgba_ub[4];
                        float rgba_f[4];

                        project_face_pixel(lt_other_tri_uv, ibuf_other, w, rgba_ub, rgba_f);

                        if (ibuf_other->rect_float) { /* from float to float */
                                mask = ((rgba_f[0] + rgba_f[1] + rgba_f[2]) * (1.0f / 3.0f)) * rgba_f[3];
                        }
                        else { /* from char to float */
                                mask = ((rgba_ub[0] + rgba_ub[1] + rgba_ub[2]) * (1.0f / (255.0f * 3.0f))) * (rgba_ub[3] * (1.0f / 255.0f));
                        }

                        BKE_image_release_ibuf(other_tpage, ibuf_other, NULL);

                        if (!ps->do_layer_stencil_inv) {
                                /* matching the gimps layer mask black/white rules, white==full opacity */
                                mask = (1.0f - mask);
                        }

                        if (mask == 0.0f) {
                                return 0.0f;
                        }
                }
                else {
                        return 0.0f;
                }
        }
        else {
                mask = 1.0f;
        }

        if (ps->do_mask_cavity) {
                const MLoopTri *lt = &ps->mlooptri_eval[tri_index];
                const int lt_vtri[3] = { PS_LOOPTRI_AS_VERT_INDEX_3(ps, lt) };
                float ca1, ca2, ca3, ca_mask;
                ca1 = ps->cavities[lt_vtri[0]];
                ca2 = ps->cavities[lt_vtri[1]];
                ca3 = ps->cavities[lt_vtri[2]];

                ca_mask = w[0] * ca1 + w[1] * ca2 + w[2] * ca3;
                ca_mask = curvemapping_evaluateF(ps->cavity_curve, 0, ca_mask);
                CLAMP(ca_mask, 0.0f, 1.0f);
                mask *= ca_mask;
        }

        /* calculate mask */
        if (ps->do_mask_normal) {
                const MLoopTri *lt = &ps->mlooptri_eval[tri_index];
                const int lt_vtri[3] = { PS_LOOPTRI_AS_VERT_INDEX_3(ps, lt) };
                const MPoly *mp = &ps->mpoly_eval[lt->poly];
                float no[3], angle_cos;

                if (mp->flag & ME_SMOOTH) {
                        const short *no1, *no2, *no3;
                        no1 = ps->mvert_eval[lt_vtri[0]].no;
                        no2 = ps->mvert_eval[lt_vtri[1]].no;
                        no3 = ps->mvert_eval[lt_vtri[2]].no;

                        no[0] = w[0] * no1[0] + w[1] * no2[0] + w[2] * no3[0];
                        no[1] = w[0] * no1[1] + w[1] * no2[1] + w[2] * no3[1];
                        no[2] = w[0] * no1[2] + w[1] * no2[2] + w[2] * no3[2];
                        normalize_v3(no);
                }
                else {
                        /* incase the */
#if 1
                        /* normalizing per pixel isn't optimal, we could cache or check ps->*/
                        normal_tri_v3(no,
                                      ps->mvert_eval[lt_vtri[0]].co,
                                      ps->mvert_eval[lt_vtri[1]].co,
                                      ps->mvert_eval[lt_vtri[2]].co);
#else
                        /* don't use because some modifiers dont have normal data (subsurf for eg) */
                        copy_v3_v3(no, (float *)ps->dm->getTessFaceData(ps->dm, tri_index, CD_NORMAL));
#endif
                }

                if (UNLIKELY(ps->is_flip_object)) {
                        negate_v3(no);
                }

                /* now we can use the normal as a mask */
                if (ps->is_ortho) {
                        angle_cos = dot_v3v3(ps->viewDir, no);
                }
                else {
                        /* Annoying but for the perspective view we need to get the pixels location in 3D space :/ */
                        float viewDirPersp[3];
                        const float *co1, *co2, *co3;
                        co1 = ps->mvert_eval[lt_vtri[0]].co;
                        co2 = ps->mvert_eval[lt_vtri[1]].co;
                        co3 = ps->mvert_eval[lt_vtri[2]].co;

                        /* Get the direction from the viewPoint to the pixel and normalize */
                        viewDirPersp[0] = (ps->viewPos[0] - (w[0] * co1[0] + w[1] * co2[0] + w[2] * co3[0]));
                        viewDirPersp[1] = (ps->viewPos[1] - (w[0] * co1[1] + w[1] * co2[1] + w[2] * co3[1]));
                        viewDirPersp[2] = (ps->viewPos[2] - (w[0] * co1[2] + w[1] * co2[2] + w[2] * co3[2]));
                        normalize_v3(viewDirPersp);
                        if (UNLIKELY(ps->is_flip_object)) {
                                negate_v3(viewDirPersp);
                        }

                        angle_cos = dot_v3v3(viewDirPersp, no);
                }

                /* If backface culling is disabled, allow painting on back faces. */
                if (!ps->do_backfacecull) {
                        angle_cos = fabsf(angle_cos);
                }

                if (angle_cos <= ps->normal_angle__cos) {
                        /* outsize the normal limit*/
                        return 0.0f;
                }
                else if (angle_cos < ps->normal_angle_inner__cos) {
                        mask *= (ps->normal_angle - acosf(angle_cos)) / ps->normal_angle_range;
                } /* otherwise no mask normal is needed, were within the limit */
        }

        /* This only works when the opacity dosnt change while painting, stylus pressure messes with this
         * so don't use it. */
        // if (ps->is_airbrush == 0) mask *= BKE_brush_alpha_get(ps->brush);

        return mask;
}

static int project_paint_pixel_sizeof(const short tool)
{
        if ((tool == PAINT_TOOL_CLONE) || (tool == PAINT_TOOL_SMEAR)) {
                return sizeof(ProjPixelClone);
        }
        else {
                return sizeof(ProjPixel);
        }
}

static int project_paint_undo_subtiles(const TileInfo *tinf, int tx, int ty)
{
        ProjPaintImage *pjIma = tinf->pjima;
        int tile_index = tx + ty * tinf->tile_width;
        bool generate_tile = false;

        /* double check lock to avoid locking */
        if (UNLIKELY(!pjIma->undoRect[tile_index])) {
                if (tinf->lock)
                        BLI_spin_lock(tinf->lock);
                if (LIKELY(!pjIma->undoRect[tile_index])) {
                        pjIma->undoRect[tile_index] = TILE_PENDING;
                        generate_tile = true;
                }
                if (tinf->lock)
                        BLI_spin_unlock(tinf->lock);
        }


        if (generate_tile) {
                ListBase *undo_tiles = ED_image_undo_get_tiles();
                volatile void *undorect;
                if (tinf->masked) {
                        undorect = image_undo_push_tile(
                                undo_tiles, pjIma->ima, pjIma->ibuf, tinf->tmpibuf,
                                tx, ty, &pjIma->maskRect[tile_index], &pjIma->valid[tile_index], true, false);
                }
                else {
                        undorect = image_undo_push_tile(
                                undo_tiles, pjIma->ima, pjIma->ibuf, tinf->tmpibuf,
                                tx, ty, NULL, &pjIma->valid[tile_index], true, false);
                }

                pjIma->ibuf->userflags |= IB_BITMAPDIRTY;
                /* tile ready, publish */
                if (tinf->lock)
                        BLI_spin_lock(tinf->lock);
                pjIma->undoRect[tile_index] = undorect;
                if (tinf->lock)
                        BLI_spin_unlock(tinf->lock);

        }

        return tile_index;
}

/* run this function when we know a bucket's, face's pixel can be initialized,
 * return the ProjPixel which is added to 'ps->bucketRect[bucket_index]' */
static ProjPixel *project_paint_uvpixel_init(
        const ProjPaintState *ps,
        MemArena *arena,
        const TileInfo *tinf,
        int x_px, int y_px,
        const float mask,
        const int tri_index,
        const float pixelScreenCo[4],
        const float world_spaceCo[3],
        const float w[3])
{
        ProjPixel *projPixel;
        int x_tile, y_tile;
        int x_round, y_round;
        int tile_offset;
        /* volatile is important here to ensure pending check is not optimized away by compiler*/
        volatile int tile_index;

        ProjPaintImage *projima = tinf->pjima;
        ImBuf *ibuf = projima->ibuf;
        /* wrap pixel location */

        x_px = mod_i(x_px, ibuf->x);
        y_px = mod_i(y_px, ibuf->y);

        BLI_assert(ps->pixel_sizeof == project_paint_pixel_sizeof(ps->tool));
        projPixel = BLI_memarena_alloc(arena, ps->pixel_sizeof);

        /* calculate the undo tile offset of the pixel, used to store the original
         * pixel color and accumulated mask if any */
        x_tile =  x_px >> IMAPAINT_TILE_BITS;
        y_tile =  y_px >> IMAPAINT_TILE_BITS;

        x_round = x_tile * IMAPAINT_TILE_SIZE;
        y_round = y_tile * IMAPAINT_TILE_SIZE;
        //memset(projPixel, 0, size);

        tile_offset = (x_px - x_round) + (y_px - y_round) * IMAPAINT_TILE_SIZE;
        tile_index = project_paint_undo_subtiles(tinf, x_tile, y_tile);

        /* other thread may be initializing the tile so wait here */
        while (projima->undoRect[tile_index] == TILE_PENDING)
                ;

        BLI_assert(tile_index < (IMAPAINT_TILE_NUMBER(ibuf->x) * IMAPAINT_TILE_NUMBER(ibuf->y)));
        BLI_assert(tile_offset < (IMAPAINT_TILE_SIZE * IMAPAINT_TILE_SIZE));

        projPixel->valid = projima->valid[tile_index];

        if (ibuf->rect_float) {
                projPixel->pixel.f_pt = ibuf->rect_float + ((x_px + y_px * ibuf->x) * 4);
                projPixel->origColor.f_pt = (float *)projima->undoRect[tile_index] + 4 * tile_offset;
                zero_v4(projPixel->newColor.f);
        }
        else {
                projPixel->pixel.ch_pt = (unsigned char *)(ibuf->rect + (x_px + y_px * ibuf->x));
                projPixel->origColor.uint_pt = (unsigned int *)projima->undoRect[tile_index] + tile_offset;
                projPixel->newColor.uint = 0;
        }

        /* screenspace unclamped, we could keep its z and w values but don't need them at the moment */
        if (ps->brush->mtex.brush_map_mode == MTEX_MAP_MODE_3D) {
                copy_v3_v3(projPixel->worldCoSS, world_spaceCo);
        }

        copy_v2_v2(projPixel->projCoSS, pixelScreenCo);

        projPixel->x_px = x_px;
        projPixel->y_px = y_px;

        projPixel->mask = (unsigned short)(mask * 65535);
        if (ps->do_masking)
                projPixel->mask_accum = projima->maskRect[tile_index] + tile_offset;
        else
                projPixel->mask_accum = NULL;

        /* which bounding box cell are we in?, needed for undo */
        projPixel->bb_cell_index = ((int)(((float)x_px / (float)ibuf->x) * PROJ_BOUNDBOX_DIV)) +
                                   ((int)(((float)y_px / (float)ibuf->y) * PROJ_BOUNDBOX_DIV)) * PROJ_BOUNDBOX_DIV;

        /* done with view3d_project_float inline */
        if (ps->tool == PAINT_TOOL_CLONE) {
                if (ps->poly_to_loop_uv_clone) {
                        ImBuf *ibuf_other;
                        Image *other_tpage = project_paint_face_clone_image(ps, tri_index);

                        if (other_tpage && (ibuf_other = BKE_image_acquire_ibuf(other_tpage, NULL, NULL))) {
                                const MLoopTri *lt_other = &ps->mlooptri_eval[tri_index];
                                const float *lt_other_tri_uv[3] = { PS_LOOPTRI_AS_UV_3(ps->poly_to_loop_uv_clone, lt_other) };

                                /* BKE_image_acquire_ibuf - TODO - this may be slow */

                                if (ibuf->rect_float) {
                                        if (ibuf_other->rect_float) { /* from float to float */
                                                project_face_pixel(lt_other_tri_uv, ibuf_other, w, NULL, ((ProjPixelClone *)projPixel)->clonepx.f);
                                        }
                                        else { /* from char to float */
                                                unsigned char rgba_ub[4];
                                                float rgba[4];
                                                project_face_pixel(lt_other_tri_uv, ibuf_other, w, rgba_ub, NULL);
                                                if (ps->use_colormanagement) {
                                                        srgb_to_linearrgb_uchar4(rgba, rgba_ub);
                                                }
                                                else {
                                                        rgba_uchar_to_float(rgba, rgba_ub);
                                                }
                                                straight_to_premul_v4_v4(((ProjPixelClone *)projPixel)->clonepx.f, rgba);
                                        }
                                }
                                else {
                                        if (ibuf_other->rect_float) { /* float to char */
                                                float rgba[4];
                                                project_face_pixel(lt_other_tri_uv, ibuf_other, w, NULL, rgba);
                                                premul_to_straight_v4(rgba);
                                                if (ps->use_colormanagement) {
                                                        linearrgb_to_srgb_uchar3(((ProjPixelClone *)projPixel)->clonepx.ch, rgba);
                                                }
                                                else {
                                                        rgb_float_to_uchar(((ProjPixelClone *)projPixel)->clonepx.ch, rgba);
                                                }
                                                ((ProjPixelClone *)projPixel)->clonepx.ch[3] =  rgba[3] * 255;
                                        }
                                        else { /* char to char */
                                                project_face_pixel(lt_other_tri_uv, ibuf_other, w, ((ProjPixelClone *)projPixel)->clonepx.ch, NULL);
                                        }
                                }

                                BKE_image_release_ibuf(other_tpage, ibuf_other, NULL);
                        }
                        else {
                                if (ibuf->rect_float) {
                                        ((ProjPixelClone *)projPixel)->clonepx.f[3] = 0;
                                }
                                else {
                                        ((ProjPixelClone *)projPixel)->clonepx.ch[3] = 0;
                                }
                        }

                }
                else {
                        float co[2];
                        sub_v2_v2v2(co, projPixel->projCoSS, ps->cloneOffset);

                        /* no need to initialize the bucket, we're only checking buckets faces and for this
                         * the faces are already initialized in project_paint_delayed_face_init(...) */
                        if (ibuf->rect_float) {
                                if (!project_paint_PickColor(ps, co, ((ProjPixelClone *)projPixel)->clonepx.f, NULL, 1)) {
                                        /* zero alpha - ignore */
                                        ((ProjPixelClone *)projPixel)->clonepx.f[3] = 0;
                                }
                        }
                        else {
                                if (!project_paint_PickColor(ps, co, NULL, ((ProjPixelClone *)projPixel)->clonepx.ch, 1)) {
                                        /* zero alpha - ignore */
                                        ((ProjPixelClone *)projPixel)->clonepx.ch[3] = 0;
                                }
                        }
                }
        }

#ifdef PROJ_DEBUG_PAINT
        if (ibuf->rect_float) projPixel->pixel.f_pt[0] = 0;
        else                  projPixel->pixel.ch_pt[0] = 0;
#endif
        /* pointer arithmetic */
        projPixel->image_index = projima - ps->projImages;

        return projPixel;
}

static bool line_clip_rect2f(
        const rctf *cliprect,
        const rctf *rect,
        const float l1[2], const float l2[2],
        float l1_clip[2], float l2_clip[2])
{
        /* first account for horizontal, then vertical lines */
        /* horiz */
        if (fabsf(l1[1] - l2[1]) < PROJ_PIXEL_TOLERANCE) {
                /* is the line out of range on its Y axis? */
                if (l1[1] < rect->ymin || l1[1] > rect->ymax) {
                        return 0;
                }
                /* line is out of range on its X axis */
                if ((l1[0] < rect->xmin && l2[0] < rect->xmin) || (l1[0] > rect->xmax && l2[0] > rect->xmax)) {
                        return 0;
                }


                /* this is a single point  (or close to)*/
                if (fabsf(l1[0] - l2[0]) < PROJ_PIXEL_TOLERANCE) {
                        if (BLI_rctf_isect_pt_v(rect, l1)) {
                                copy_v2_v2(l1_clip, l1);
                                copy_v2_v2(l2_clip, l2);
                                return 1;
                        }
                        else {
                                return 0;
                        }
                }

                copy_v2_v2(l1_clip, l1);
                copy_v2_v2(l2_clip, l2);
                CLAMP(l1_clip[0], rect->xmin, rect->xmax);
                CLAMP(l2_clip[0], rect->xmin, rect->xmax);
                return 1;
        }
        else if (fabsf(l1[0] - l2[0]) < PROJ_PIXEL_TOLERANCE) {
                /* is the line out of range on its X axis? */
                if (l1[0] < rect->xmin || l1[0] > rect->xmax) {
                        return 0;
                }

                /* line is out of range on its Y axis */
                if ((l1[1] < rect->ymin && l2[1] < rect->ymin) || (l1[1] > rect->ymax && l2[1] > rect->ymax)) {
                        return 0;
                }

                /* this is a single point  (or close to)*/
                if (fabsf(l1[1] - l2[1]) < PROJ_PIXEL_TOLERANCE) {
                        if (BLI_rctf_isect_pt_v(rect, l1)) {
                                copy_v2_v2(l1_clip, l1);
                                copy_v2_v2(l2_clip, l2);
                                return 1;
                        }
                        else {
                                return 0;
                        }
                }

                copy_v2_v2(l1_clip, l1);
                copy_v2_v2(l2_clip, l2);
                CLAMP(l1_clip[1], rect->ymin, rect->ymax);
                CLAMP(l2_clip[1], rect->ymin, rect->ymax);
                return 1;
        }
        else {
                float isect;
                short ok1 = 0;
                short ok2 = 0;

                /* Done with vertical lines */

                /* are either of the points inside the rectangle ? */
                if (BLI_rctf_isect_pt_v(rect, l1)) {
                        copy_v2_v2(l1_clip, l1);
                        ok1 = 1;
                }

                if (BLI_rctf_isect_pt_v(rect, l2)) {
                        copy_v2_v2(l2_clip, l2);
                        ok2 = 1;
                }

                /* line inside rect */
                if (ok1 && ok2) return 1;

                /* top/bottom */
                if (line_isect_y(l1, l2, rect->ymin, &isect) && (isect >= cliprect->xmin) && (isect <= cliprect->xmax)) {
                        if (l1[1] < l2[1]) { /* line 1 is outside */
                                l1_clip[0] = isect;
                                l1_clip[1] = rect->ymin;
                                ok1 = 1;
                        }
                        else {
                                l2_clip[0] = isect;
                                l2_clip[1] = rect->ymin;
                                ok2 = 2;
                        }
                }

                if (ok1 && ok2) return 1;

                if (line_isect_y(l1, l2, rect->ymax, &isect) && (isect >= cliprect->xmin) && (isect <= cliprect->xmax)) {
                        if (l1[1] > l2[1]) { /* line 1 is outside */
                                l1_clip[0] = isect;
                                l1_clip[1] = rect->ymax;
                                ok1 = 1;
                        }
                        else {
                                l2_clip[0] = isect;
                                l2_clip[1] = rect->ymax;
                                ok2 = 2;
                        }
                }

                if (ok1 && ok2) return 1;

                /* left/right */
                if (line_isect_x(l1, l2, rect->xmin, &isect) && (isect >= cliprect->ymin) && (isect <= cliprect->ymax)) {
                        if (l1[0] < l2[0]) { /* line 1 is outside */
                                l1_clip[0] = rect->xmin;
                                l1_clip[1] = isect;
                                ok1 = 1;
                        }
                        else {
                                l2_clip[0] = rect->xmin;
                                l2_clip[1] = isect;
                                ok2 = 2;
                        }
                }

                if (ok1 && ok2) return 1;

                if (line_isect_x(l1, l2, rect->xmax, &isect) && (isect >= cliprect->ymin) && (isect <= cliprect->ymax)) {
                        if (l1[0] > l2[0]) { /* line 1 is outside */
                                l1_clip[0] = rect->xmax;
                                l1_clip[1] = isect;
                                ok1 = 1;
                        }
                        else {
                                l2_clip[0] = rect->xmax;
                                l2_clip[1] = isect;
                                ok2 = 2;
                        }
                }

                if (ok1 && ok2) {
                        return 1;
                }
                else {
                        return 0;
                }
        }
}



/**
 * Scale the tri about its center
 * scaling by #PROJ_FACE_SCALE_SEAM (0.99x) is used for getting fake UV pixel coords that are on the
 * edge of the face but slightly inside it occlusion tests don't return hits on adjacent faces
 */
#ifndef PROJ_DEBUG_NOSEAMBLEED

static void scale_tri(float insetCos[3][3], const float *origCos[4], const float inset)
{
        float cent[3];
        cent[0] = (origCos[0][0] + origCos[1][0] + origCos[2][0]) * (1.0f / 3.0f);
        cent[1] = (origCos[0][1] + origCos[1][1] + origCos[2][1]) * (1.0f / 3.0f);
        cent[2] = (origCos[0][2] + origCos[1][2] + origCos[2][2]) * (1.0f / 3.0f);

        sub_v3_v3v3(insetCos[0], origCos[0], cent);
        sub_v3_v3v3(insetCos[1], origCos[1], cent);
        sub_v3_v3v3(insetCos[2], origCos[2], cent);

        mul_v3_fl(insetCos[0], inset);
        mul_v3_fl(insetCos[1], inset);
        mul_v3_fl(insetCos[2], inset);

        add_v3_v3(insetCos[0], cent);
        add_v3_v3(insetCos[1], cent);
        add_v3_v3(insetCos[2], cent);
}
#endif //PROJ_DEBUG_NOSEAMBLEED

static float len_squared_v2v2_alt(const float v1[2], const float v2_1, const float v2_2)
{
        float x, y;

        x = v1[0] - v2_1;
        y = v1[1] - v2_2;
        return x * x + y * y;
}

/* note, use a squared value so we can use len_squared_v2v2
 * be sure that you have done a bounds check first or this may fail */
/* only give bucket_bounds as an arg because we need it elsewhere */
static bool project_bucket_isect_circle(const float cent[2], const float radius_squared, const rctf *bucket_bounds)
{

        /* Would normally to a simple intersection test, however we know the bounds of these 2 already intersect
         * so we only need to test if the center is inside the vertical or horizontal bounds on either axis,
         * this is even less work then an intersection test
         */
#if 0
        if (BLI_rctf_isect_pt_v(bucket_bounds, cent))
                return 1;
#endif

        if ((bucket_bounds->xmin <= cent[0] && bucket_bounds->xmax >= cent[0]) ||
            (bucket_bounds->ymin <= cent[1] && bucket_bounds->ymax >= cent[1]))
        {
                return 1;
        }

        /* out of bounds left */
        if (cent[0] < bucket_bounds->xmin) {
                /* lower left out of radius test */
                if (cent[1] < bucket_bounds->ymin) {
                        return (len_squared_v2v2_alt(cent, bucket_bounds->xmin, bucket_bounds->ymin) < radius_squared) ? 1 : 0;
                }
                /* top left test */
                else if (cent[1] > bucket_bounds->ymax) {
                        return (len_squared_v2v2_alt(cent, bucket_bounds->xmin, bucket_bounds->ymax) < radius_squared) ? 1 : 0;
                }
        }
        else if (cent[0] > bucket_bounds->xmax) {
                /* lower right out of radius test */
                if (cent[1] < bucket_bounds->ymin) {
                        return (len_squared_v2v2_alt(cent, bucket_bounds->xmax, bucket_bounds->ymin) < radius_squared) ? 1 : 0;
                }
                /* top right test */
                else if (cent[1] > bucket_bounds->ymax) {
                        return (len_squared_v2v2_alt(cent, bucket_bounds->xmax, bucket_bounds->ymax) < radius_squared) ? 1 : 0;
                }
        }

        return 0;
}



/* Note for rect_to_uvspace_ortho() and rect_to_uvspace_persp()
 * in ortho view this function gives good results when bucket_bounds are outside the triangle
 * however in some cases, perspective view will mess up with faces that have minimal screenspace area
 * (viewed from the side)
 *
 * for this reason its not reliable in this case so we'll use the Simple Barycentric'
 * funcs that only account for points inside the triangle.
 * however switching back to this for ortho is always an option */

static void rect_to_uvspace_ortho(
        const rctf *bucket_bounds,
        const float *v1coSS, const float *v2coSS, const float *v3coSS,
        const float *uv1co, const float *uv2co, const float *uv3co,
        float bucket_bounds_uv[4][2],
        const int flip)
{
        float uv[2];
        float w[3];

        /* get the UV space bounding box */
        uv[0] = bucket_bounds->xmax;
        uv[1] = bucket_bounds->ymin;
        barycentric_weights_v2(v1coSS, v2coSS, v3coSS, uv, w);
        interp_v2_v2v2v2(bucket_bounds_uv[flip ? 3 : 0], uv1co, uv2co, uv3co, w);

        //uv[0] = bucket_bounds->xmax; // set above
        uv[1] = bucket_bounds->ymax;
        barycentric_weights_v2(v1coSS, v2coSS, v3coSS, uv, w);
        interp_v2_v2v2v2(bucket_bounds_uv[flip ? 2 : 1], uv1co, uv2co, uv3co, w);

        uv[0] = bucket_bounds->xmin;
        //uv[1] = bucket_bounds->ymax; // set above
        barycentric_weights_v2(v1coSS, v2coSS, v3coSS, uv, w);
        interp_v2_v2v2v2(bucket_bounds_uv[flip ? 1 : 2], uv1co, uv2co, uv3co, w);

        //uv[0] = bucket_bounds->xmin; // set above
        uv[1] = bucket_bounds->ymin;
        barycentric_weights_v2(v1coSS, v2coSS, v3coSS, uv, w);
        interp_v2_v2v2v2(bucket_bounds_uv[flip ? 0 : 3], uv1co, uv2co, uv3co, w);
}

/* same as above but use barycentric_weights_v2_persp */
static void rect_to_uvspace_persp(
        const rctf *bucket_bounds,
        const float *v1coSS, const float *v2coSS, const float *v3coSS,
        const float *uv1co, const float *uv2co, const float *uv3co,
        float bucket_bounds_uv[4][2],
        const int flip
        )
{
        float uv[2];
        float w[3];

        /* get the UV space bounding box */
        uv[0] = bucket_bounds->xmax;
        uv[1] = bucket_bounds->ymin;
        barycentric_weights_v2_persp(v1coSS, v2coSS, v3coSS, uv, w);
        interp_v2_v2v2v2(bucket_bounds_uv[flip ? 3 : 0], uv1co, uv2co, uv3co, w);

        //uv[0] = bucket_bounds->xmax; // set above
        uv[1] = bucket_bounds->ymax;
        barycentric_weights_v2_persp(v1coSS, v2coSS, v3coSS, uv, w);
        interp_v2_v2v2v2(bucket_bounds_uv[flip ? 2 : 1], uv1co, uv2co, uv3co, w);

        uv[0] = bucket_bounds->xmin;
        //uv[1] = bucket_bounds->ymax; // set above
        barycentric_weights_v2_persp(v1coSS, v2coSS, v3coSS, uv, w);
        interp_v2_v2v2v2(bucket_bounds_uv[flip ? 1 : 2], uv1co, uv2co, uv3co, w);

        //uv[0] = bucket_bounds->xmin; // set above
        uv[1] = bucket_bounds->ymin;
        barycentric_weights_v2_persp(v1coSS, v2coSS, v3coSS, uv, w);
        interp_v2_v2v2v2(bucket_bounds_uv[flip ? 0 : 3], uv1co, uv2co, uv3co, w);
}

/* This works as we need it to but we can save a few steps and not use it */

#if 0
static float angle_2d_clockwise(const float p1[2], const float p2[2], const float p3[2])
{
        float v1[2], v2[2];

        v1[0] = p1[0] - p2[0];    v1[1] = p1[1] - p2[1];
        v2[0] = p3[0] - p2[0];    v2[1] = p3[1] - p2[1];

        return -atan2f(v1[0] * v2[1] - v1[1] * v2[0], v1[0] * v2[0] + v1[1] * v2[1]);
}
#endif

#define ISECT_1 (1)
#define ISECT_2 (1 << 1)
#define ISECT_3 (1 << 2)
#define ISECT_4 (1 << 3)
#define ISECT_ALL3 ((1 << 3) - 1)
#define ISECT_ALL4 ((1 << 4) - 1)

/* limit must be a fraction over 1.0f */
static bool IsectPT2Df_limit(
        const float pt[2],
        const float v1[2], const float v2[2], const float v3[2],
        const float limit)
{
        return ((area_tri_v2(pt, v1, v2) +
                 area_tri_v2(pt, v2, v3) +
                 area_tri_v2(pt, v3, v1)) / (area_tri_v2(v1, v2, v3))) < limit;
}

/* Clip the face by a bucket and set the uv-space bucket_bounds_uv
 * so we have the clipped UV's to do pixel intersection tests with
 * */
static int float_z_sort_flip(const void *p1, const void *p2)
{
        return (((float *)p1)[2] < ((float *)p2)[2] ? 1 : -1);
}

static int float_z_sort(const void *p1, const void *p2)
{
        return (((float *)p1)[2] < ((float *)p2)[2] ? -1 : 1);
}

/* assumes one point is within the rectangle */
static bool line_rect_clip(
        const rctf *rect,
        const float l1[4], const float l2[4],
        const float uv1[2], const float uv2[2],
        float uv[2], bool is_ortho)
{
        float min = FLT_MAX, tmp;
        float xlen = l2[0] - l1[0];
        float ylen = l2[1] - l1[1];

        /* 0.1 might seem too much, but remember, this is pixels! */
        if (xlen > 0.1f) {
                if ((l1[0] - rect->xmin) * (l2[0] - rect->xmin) <= 0) {
                        tmp = rect->xmin;
                        min = min_ff((tmp - l1[0]) / xlen, min);
                }
                else if ((l1[0] - rect->xmax) * (l2[0] - rect->xmax) < 0) {
                        tmp = rect->xmax;
                        min = min_ff((tmp - l1[0]) / xlen, min);
                }
        }

        if (ylen > 0.1f) {
                if ((l1[1] - rect->ymin) * (l2[1] - rect->ymin) <= 0) {
                        tmp = rect->ymin;
                        min = min_ff((tmp - l1[1]) / ylen, min);
                }
                else if ((l1[1] - rect->ymax) * (l2[1] - rect->ymax) < 0) {
                        tmp = rect->ymax;
                        min = min_ff((tmp - l1[1]) / ylen, min);
                }
        }

        if (min == FLT_MAX)
                return false;

        tmp = (is_ortho) ? 1.0f : (l1[3] + min * (l2[3] - l1[3]));

        uv[0] = (uv1[0] + min / tmp * (uv2[0] - uv1[0]));
        uv[1] = (uv1[1] + min / tmp * (uv2[1] - uv1[1]));

        return true;
}


static void project_bucket_clip_face(
        const bool is_ortho, const bool is_flip_object,
        const rctf *cliprect,
        const rctf *bucket_bounds,
        const float *v1coSS, const float *v2coSS, const float *v3coSS,
        const float *uv1co, const float *uv2co, const float *uv3co,
        float bucket_bounds_uv[8][2],
        int *tot, bool cull)
{
        int inside_bucket_flag = 0;
        int inside_face_flag = 0;
        int flip;
        bool collinear = false;

        float bucket_bounds_ss[4][2];

        /* detect pathological case where face the three vertices are almost collinear in screen space.
         * mostly those will be culled but when flood filling or with
         * smooth shading it's a possibility */
        if (min_fff(dist_squared_to_line_v2(v1coSS, v2coSS, v3coSS),
                    dist_squared_to_line_v2(v2coSS, v3coSS, v1coSS),
                    dist_squared_to_line_v2(v3coSS, v1coSS, v2coSS)) < PROJ_PIXEL_TOLERANCE)
        {
                collinear = true;
        }

        /* get the UV space bounding box */
        inside_bucket_flag |= BLI_rctf_isect_pt_v(bucket_bounds, v1coSS);
        inside_bucket_flag |= BLI_rctf_isect_pt_v(bucket_bounds, v2coSS) << 1;
        inside_bucket_flag |= BLI_rctf_isect_pt_v(bucket_bounds, v3coSS) << 2;

        if (inside_bucket_flag == ISECT_ALL3) {
                /* is_flip_object is used here because we use the face winding */
                flip = (((line_point_side_v2(v1coSS, v2coSS, v3coSS) > 0.0f) != is_flip_object) !=
                        (line_point_side_v2(uv1co, uv2co, uv3co) > 0.0f));

                /* all screenspace points are inside the bucket bounding box,
                 * this means we don't need to clip and can simply return the UVs */
                if (flip) { /* facing the back? */
                        copy_v2_v2(bucket_bounds_uv[0], uv3co);
                        copy_v2_v2(bucket_bounds_uv[1], uv2co);
                        copy_v2_v2(bucket_bounds_uv[2], uv1co);
                }
                else {
                        copy_v2_v2(bucket_bounds_uv[0], uv1co);
                        copy_v2_v2(bucket_bounds_uv[1], uv2co);
                        copy_v2_v2(bucket_bounds_uv[2], uv3co);
                }

                *tot = 3;
                return;
        }
        /* handle pathological case here,
         * no need for further intersections below since tringle area is almost zero */
        if (collinear) {
                int flag;

                (*tot) = 0;

                if (cull)
                        return;

                if (inside_bucket_flag & ISECT_1) { copy_v2_v2(bucket_bounds_uv[*tot], uv1co); (*tot)++; }

                flag = inside_bucket_flag & (ISECT_1 | ISECT_2);
                if (flag && flag != (ISECT_1 | ISECT_2)) {
                        if (line_rect_clip(bucket_bounds, v1coSS, v2coSS, uv1co, uv2co, bucket_bounds_uv[*tot], is_ortho))
                                (*tot)++;
                }

                if (inside_bucket_flag & ISECT_2) { copy_v2_v2(bucket_bounds_uv[*tot], uv2co); (*tot)++; }

                flag = inside_bucket_flag & (ISECT_2 | ISECT_3);
                if (flag && flag != (ISECT_2 | ISECT_3)) {
                        if (line_rect_clip(bucket_bounds, v2coSS, v3coSS, uv2co, uv3co, bucket_bounds_uv[*tot], is_ortho))
                                (*tot)++;
                }

                if (inside_bucket_flag & ISECT_3) { copy_v2_v2(bucket_bounds_uv[*tot], uv3co); (*tot)++; }

                flag = inside_bucket_flag & (ISECT_3 | ISECT_1);
                if (flag && flag != (ISECT_3 | ISECT_1)) {
                        if (line_rect_clip(bucket_bounds, v3coSS, v1coSS, uv3co, uv1co, bucket_bounds_uv[*tot], is_ortho))
                                (*tot)++;
                }

                if ((*tot) < 3) {
                        /* no intersections to speak of, but more probable is that all face is just outside the
                         * rectangle and culled due to float precision issues. Since above tests have failed,
                         * just dump triangle as is for painting */
                        *tot = 0;
                        copy_v2_v2(bucket_bounds_uv[*tot], uv1co); (*tot)++;
                        copy_v2_v2(bucket_bounds_uv[*tot], uv2co); (*tot)++;
                        copy_v2_v2(bucket_bounds_uv[*tot], uv3co); (*tot)++;
                        return;
                }

                return;
        }

        /* get the UV space bounding box */
        /* use IsectPT2Df_limit here so we catch points are are touching the tri edge
         * (or a small fraction over) */
        bucket_bounds_ss[0][0] = bucket_bounds->xmax;
        bucket_bounds_ss[0][1] = bucket_bounds->ymin;
        inside_face_flag |= (IsectPT2Df_limit(bucket_bounds_ss[0], v1coSS, v2coSS, v3coSS, 1 + PROJ_GEOM_TOLERANCE) ? ISECT_1 : 0);

        bucket_bounds_ss[1][0] = bucket_bounds->xmax;
        bucket_bounds_ss[1][1] = bucket_bounds->ymax;
        inside_face_flag |= (IsectPT2Df_limit(bucket_bounds_ss[1], v1coSS, v2coSS, v3coSS, 1 + PROJ_GEOM_TOLERANCE) ? ISECT_2 : 0);

        bucket_bounds_ss[2][0] = bucket_bounds->xmin;
        bucket_bounds_ss[2][1] = bucket_bounds->ymax;
        inside_face_flag |= (IsectPT2Df_limit(bucket_bounds_ss[2], v1coSS, v2coSS, v3coSS, 1 + PROJ_GEOM_TOLERANCE) ? ISECT_3 : 0);

        bucket_bounds_ss[3][0] = bucket_bounds->xmin;
        bucket_bounds_ss[3][1] = bucket_bounds->ymin;
        inside_face_flag |= (IsectPT2Df_limit(bucket_bounds_ss[3], v1coSS, v2coSS, v3coSS, 1 + PROJ_GEOM_TOLERANCE) ? ISECT_4 : 0);

        flip = ((line_point_side_v2(v1coSS, v2coSS, v3coSS) > 0.0f) !=
                (line_point_side_v2(uv1co, uv2co, uv3co) > 0.0f));

        if (inside_face_flag == ISECT_ALL4) {
                /* bucket is totally inside the screenspace face, we can safely use weights */

                if (is_ortho) {
                        rect_to_uvspace_ortho(bucket_bounds, v1coSS, v2coSS, v3coSS, uv1co, uv2co, uv3co, bucket_bounds_uv, flip);
                }
                else {
                        rect_to_uvspace_persp(bucket_bounds, v1coSS, v2coSS, v3coSS, uv1co, uv2co, uv3co, bucket_bounds_uv, flip);
                }

                *tot = 4;
                return;
        }
        else {
                /* The Complicated Case!
                 *
                 * The 2 cases above are where the face is inside the bucket
                 * or the bucket is inside the face.
                 *
                 * we need to make a convex polyline from the intersection between the screenspace face
                 * and the bucket bounds.
                 *
                 * There are a number of ways this could be done, currently it just collects all
                 * intersecting verts, and line intersections, then sorts them clockwise, this is
                 * a lot easier then evaluating the geometry to do a correct clipping on both shapes.
                 */


                /* Add a bunch of points, we know must make up the convex hull
                 * which is the clipped rect and triangle */

                /* Maximum possible 6 intersections when using a rectangle and triangle */

                /* The 3rd float is used to store angle for qsort(), NOT as a Z location */
                float isectVCosSS[8][3];
                float v1_clipSS[2], v2_clipSS[2];
                float w[3];

                /* calc center */
                float cent[2] = {0.0f, 0.0f};
                /*float up[2] = {0.0f, 1.0f};*/
                int i;
                bool doubles;

                (*tot) = 0;

                if (inside_face_flag & ISECT_1) { copy_v2_v2(isectVCosSS[*tot], bucket_bounds_ss[0]); (*tot)++; }
                if (inside_face_flag & ISECT_2) { copy_v2_v2(isectVCosSS[*tot], bucket_bounds_ss[1]); (*tot)++; }
                if (inside_face_flag & ISECT_3) { copy_v2_v2(isectVCosSS[*tot], bucket_bounds_ss[2]); (*tot)++; }
                if (inside_face_flag & ISECT_4) { copy_v2_v2(isectVCosSS[*tot], bucket_bounds_ss[3]); (*tot)++; }

                if (inside_bucket_flag & ISECT_1) { copy_v2_v2(isectVCosSS[*tot], v1coSS); (*tot)++; }
                if (inside_bucket_flag & ISECT_2) { copy_v2_v2(isectVCosSS[*tot], v2coSS); (*tot)++; }
                if (inside_bucket_flag & ISECT_3) { copy_v2_v2(isectVCosSS[*tot], v3coSS); (*tot)++; }

                if ((inside_bucket_flag & (ISECT_1 | ISECT_2)) != (ISECT_1 | ISECT_2)) {
                        if (line_clip_rect2f(cliprect, bucket_bounds, v1coSS, v2coSS, v1_clipSS, v2_clipSS)) {
                                if ((inside_bucket_flag & ISECT_1) == 0) { copy_v2_v2(isectVCosSS[*tot], v1_clipSS); (*tot)++; }
                                if ((inside_bucket_flag & ISECT_2) == 0) { copy_v2_v2(isectVCosSS[*tot], v2_clipSS); (*tot)++; }
                        }
                }

                if ((inside_bucket_flag & (ISECT_2 | ISECT_3)) != (ISECT_2 | ISECT_3)) {
                        if (line_clip_rect2f(cliprect, bucket_bounds, v2coSS, v3coSS, v1_clipSS, v2_clipSS)) {
                                if ((inside_bucket_flag & ISECT_2) == 0) { copy_v2_v2(isectVCosSS[*tot], v1_clipSS); (*tot)++; }
                                if ((inside_bucket_flag & ISECT_3) == 0) { copy_v2_v2(isectVCosSS[*tot], v2_clipSS); (*tot)++; }
                        }
                }

                if ((inside_bucket_flag & (ISECT_3 | ISECT_1)) != (ISECT_3 | ISECT_1)) {
                        if (line_clip_rect2f(cliprect, bucket_bounds, v3coSS, v1coSS, v1_clipSS, v2_clipSS)) {
                                if ((inside_bucket_flag & ISECT_3) == 0) { copy_v2_v2(isectVCosSS[*tot], v1_clipSS); (*tot)++; }
                                if ((inside_bucket_flag & ISECT_1) == 0) { copy_v2_v2(isectVCosSS[*tot], v2_clipSS); (*tot)++; }
                        }
                }


                if ((*tot) < 3) { /* no intersections to speak of */
                        *tot = 0;
                        return;
                }

                /* now we have all points we need, collect their angles and sort them clockwise */

                for (i = 0; i < (*tot); i++) {
                        cent[0] += isectVCosSS[i][0];
                        cent[1] += isectVCosSS[i][1];
                }
                cent[0] = cent[0] / (float)(*tot);
                cent[1] = cent[1] / (float)(*tot);



                /* Collect angles for every point around the center point */


#if 0   /* uses a few more cycles then the above loop */
                for (i = 0; i < (*tot); i++) {
                        isectVCosSS[i][2] = angle_2d_clockwise(up, cent, isectVCosSS[i]);
                }
#endif

                /* Abuse this var for the loop below */
                v1_clipSS[0] = cent[0];
                v1_clipSS[1] = cent[1] + 1.0f;

                for (i = 0; i < (*tot); i++) {
                        v2_clipSS[0] = isectVCosSS[i][0] - cent[0];
                        v2_clipSS[1] = isectVCosSS[i][1] - cent[1];
                        isectVCosSS[i][2] = atan2f(v1_clipSS[0] * v2_clipSS[1] - v1_clipSS[1] * v2_clipSS[0],
                                                   v1_clipSS[0] * v2_clipSS[0] + v1_clipSS[1] * v2_clipSS[1]);
                }

                if (flip) qsort(isectVCosSS, *tot, sizeof(float) * 3, float_z_sort_flip);
                else      qsort(isectVCosSS, *tot, sizeof(float) * 3, float_z_sort);

                doubles = true;
                while (doubles == true) {
                        doubles = false;

                        for (i = 0; i < (*tot); i++) {
                                if (fabsf(isectVCosSS[(i + 1) % *tot][0] - isectVCosSS[i][0]) < PROJ_PIXEL_TOLERANCE &&
                                    fabsf(isectVCosSS[(i + 1) % *tot][1] - isectVCosSS[i][1]) < PROJ_PIXEL_TOLERANCE)
                                {
                                        int j;
                                        for (j = i; j < (*tot) - 1; j++) {
                                                isectVCosSS[j][0] = isectVCosSS[j + 1][0];
                                                isectVCosSS[j][1] = isectVCosSS[j + 1][1];
                                        }
                                        /* keep looking for more doubles */
                                        doubles = true;
                                        (*tot)--;
                                }
                        }

                        /* its possible there is only a few left after remove doubles */
                        if ((*tot) < 3) {
                                // printf("removed too many doubles B\n");
                                *tot = 0;
                                return;
                        }
                }

                if (is_ortho) {
                        for (i = 0; i < (*tot); i++) {
                                barycentric_weights_v2(v1coSS, v2coSS, v3coSS, isectVCosSS[i], w);
                                interp_v2_v2v2v2(bucket_bounds_uv[i], uv1co, uv2co, uv3co, w);
                        }
                }
                else {
                        for (i = 0; i < (*tot); i++) {
                                barycentric_weights_v2_persp(v1coSS, v2coSS, v3coSS, isectVCosSS[i], w);
                                interp_v2_v2v2v2(bucket_bounds_uv[i], uv1co, uv2co, uv3co, w);
                        }
                }
        }

#ifdef PROJ_DEBUG_PRINT_CLIP
        /* include this at the bottom of the above function to debug the output */

        {
                /* If there are ever any problems, */
                float test_uv[4][2];
                int i;
                if (is_ortho) rect_to_uvspace_ortho(bucket_bounds, v1coSS, v2coSS, v3coSS, uv1co, uv2co, uv3co, test_uv, flip);
                else          rect_to_uvspace_persp(bucket_bounds, v1coSS, v2coSS, v3coSS, uv1co, uv2co, uv3co, test_uv, flip);
                printf("(  [(%f,%f), (%f,%f), (%f,%f), (%f,%f)], ",
                       test_uv[0][0], test_uv[0][1],   test_uv[1][0], test_uv[1][1],
                       test_uv[2][0], test_uv[2][1],    test_uv[3][0], test_uv[3][1]);

                printf("  [(%f,%f), (%f,%f), (%f,%f)], ", uv1co[0], uv1co[1],   uv2co[0], uv2co[1],    uv3co[0], uv3co[1]);

                printf("[");
                for (i = 0; i < (*tot); i++) {
                        printf("(%f, %f),", bucket_bounds_uv[i][0], bucket_bounds_uv[i][1]);
                }
                printf("]),\\\n");
        }
#endif
}

/*
 * # This script creates faces in a blender scene from printed data above.
 *
 * project_ls = [
 * ...(output from above block)...
 * ]
 *
 * from Blender import Scene, Mesh, Window, sys, Mathutils
 *
 * import bpy
 *
 * V = Mathutils.Vector
 *
 * def main():
 *     sce = bpy.data.scenes.active
 *
 *     for item in project_ls:
 *         bb = item[0]
 *         uv = item[1]
 *         poly = item[2]
 *
 *         me = bpy.data.meshes.new()
 *         ob = sce.objects.new(me)
 *
 *         me.verts.extend([V(bb[0]).xyz, V(bb[1]).xyz, V(bb[2]).xyz, V(bb[3]).xyz])
 *         me.faces.extend([(0,1,2,3),])
 *         me.verts.extend([V(uv[0]).xyz, V(uv[1]).xyz, V(uv[2]).xyz])
 *         me.faces.extend([(4,5,6),])
 *
 *         vs = [V(p).xyz for p in poly]
 *         print len(vs)
 *         l = len(me.verts)
 *         me.verts.extend(vs)
 *
 *         i = l
 *         while i < len(me.verts):
 *             ii = i + 1
 *             if ii == len(me.verts):
 *                 ii = l
 *             me.edges.extend([i, ii])
 *             i += 1
 *
 * if __name__ == '__main__':
 *     main()
 */


#undef ISECT_1
#undef ISECT_2
#undef ISECT_3
#undef ISECT_4
#undef ISECT_ALL3
#undef ISECT_ALL4


/* checks if pt is inside a convex 2D polyline, the polyline must be ordered rotating clockwise
 * otherwise it would have to test for mixed (line_point_side_v2 > 0.0f) cases */
static bool IsectPoly2Df(const float pt[2], float uv[][2], const int tot)
{
        int i;
        if (line_point_side_v2(uv[tot - 1], uv[0], pt) < 0.0f)
                return 0;

        for (i = 1; i < tot; i++) {
                if (line_point_side_v2(uv[i - 1], uv[i], pt) < 0.0f)
                        return 0;

        }

        return 1;
}
static bool IsectPoly2Df_twoside(const float pt[2], float uv[][2], const int tot)
{
        int i;
        bool side = (line_point_side_v2(uv[tot - 1], uv[0], pt) > 0.0f);

        for (i = 1; i < tot; i++) {
                if ((line_point_side_v2(uv[i - 1], uv[i], pt) > 0.0f) != side)
                        return 0;

        }

        return 1;
}

/* One of the most important function for projection painting,
 * since it selects the pixels to be added into each bucket.
 *
 * initialize pixels from this face where it intersects with the bucket_index,
 * optionally initialize pixels for removing seams */
static void project_paint_face_init(
        const ProjPaintState *ps,
        const int thread_index, const int bucket_index, const int tri_index, const int image_index,
        const rctf *clip_rect, const rctf *bucket_bounds, ImBuf *ibuf, ImBuf **tmpibuf)
{
        /* Projection vars, to get the 3D locations into screen space  */
        MemArena *arena = ps->arena_mt[thread_index];
        LinkNode **bucketPixelNodes = ps->bucketRect + bucket_index;
        LinkNode *bucketFaceNodes = ps->bucketFaces[bucket_index];
        bool threaded = (ps->thread_tot > 1);

        TileInfo tinf = {
                ps->tile_lock,
                ps->do_masking,
                IMAPAINT_TILE_NUMBER(ibuf->x),
                tmpibuf,
                ps->projImages + image_index,
        };

        const MLoopTri *lt = &ps->mlooptri_eval[tri_index];
        const int lt_vtri[3] = { PS_LOOPTRI_AS_VERT_INDEX_3(ps, lt) };
        const float *lt_tri_uv[3] = { PS_LOOPTRI_AS_UV_3(ps->poly_to_loop_uv, lt) };

        /* UV/pixel seeking data */
        /* Image X/Y-Pixel */
        int x, y;
        float mask;
        /* Image floating point UV - same as x, y but from 0.0-1.0 */
        float uv[2];

        /* vert co screen-space, these will be assigned to lt_vtri[0-2] */
        const float *v1coSS, *v2coSS, *v3coSS;

        /* vertex screenspace coords */
        const float *vCo[3];

        float w[3], wco[3];

        /* for convenience only, these will be assigned to lt_tri_uv[0],1,2 or lt_tri_uv[0],2,3 */
        float *uv1co, *uv2co, *uv3co;
        float pixelScreenCo[4];
        bool do_3d_mapping = ps->brush->mtex.brush_map_mode == MTEX_MAP_MODE_3D;

        /* ispace bounds */
        rcti bounds_px;
        /* vars for getting uvspace bounds */

        /* bucket bounds in UV space so we can init pixels only for this face,  */
        float lt_uv_pxoffset[3][2];
        float xhalfpx, yhalfpx;
        const float ibuf_xf = (float)ibuf->x, ibuf_yf = (float)ibuf->y;

        /* for early loop exit */
        int has_x_isect = 0, has_isect = 0;

        float uv_clip[8][2];
        int uv_clip_tot;
        const bool is_ortho = ps->is_ortho;
        const bool is_flip_object = ps->is_flip_object;
        const bool do_backfacecull = ps->do_backfacecull;
        const bool do_clip = ps->rv3d ? ps->rv3d->rflag & RV3D_CLIPPING : 0;

        vCo[0] = ps->mvert_eval[lt_vtri[0]].co;
        vCo[1] = ps->mvert_eval[lt_vtri[1]].co;
        vCo[2] = ps->mvert_eval[lt_vtri[2]].co;


        /* Use lt_uv_pxoffset instead of lt_tri_uv so we can offset the UV half a pixel
         * this is done so we can avoid offsetting all the pixels by 0.5 which causes
         * problems when wrapping negative coords */
        xhalfpx = (0.5f + (PROJ_PIXEL_TOLERANCE * (1.0f / 3.0f))) / ibuf_xf;
        yhalfpx = (0.5f + (PROJ_PIXEL_TOLERANCE * (1.0f / 4.0f))) / ibuf_yf;

        /* Note about (PROJ_GEOM_TOLERANCE/x) above...
         * Needed to add this offset since UV coords are often quads aligned to pixels.
         * In this case pixels can be exactly between 2 triangles causing nasty
         * artifacts.
         *
         * This workaround can be removed and painting will still work on most cases
         * but since the first thing most people try is painting onto a quad- better make it work.
         */

        lt_uv_pxoffset[0][0] = lt_tri_uv[0][0] - xhalfpx;
        lt_uv_pxoffset[0][1] = lt_tri_uv[0][1] - yhalfpx;

        lt_uv_pxoffset[1][0] = lt_tri_uv[1][0] - xhalfpx;
        lt_uv_pxoffset[1][1] = lt_tri_uv[1][1] - yhalfpx;

        lt_uv_pxoffset[2][0] = lt_tri_uv[2][0] - xhalfpx;
        lt_uv_pxoffset[2][1] = lt_tri_uv[2][1] - yhalfpx;

        {
                uv1co = lt_uv_pxoffset[0]; // was lt_tri_uv[i1];
                uv2co = lt_uv_pxoffset[1]; // was lt_tri_uv[i2];
                uv3co = lt_uv_pxoffset[2]; // was lt_tri_uv[i3];

                v1coSS = ps->screenCoords[lt_vtri[0]];
                v2coSS = ps->screenCoords[lt_vtri[1]];
                v3coSS = ps->screenCoords[lt_vtri[2]];

                /* This function gives is a concave polyline in UV space from the clipped tri*/
                project_bucket_clip_face(
                        is_ortho, is_flip_object,
                        clip_rect, bucket_bounds,
                        v1coSS, v2coSS, v3coSS,
                        uv1co, uv2co, uv3co,
                        uv_clip, &uv_clip_tot,
                        do_backfacecull || ps->do_occlude);

                /* sometimes this happens, better just allow for 8 intersectiosn even though there should be max 6 */
#if 0
                if (uv_clip_tot > 6) {
                        printf("this should never happen! %d\n", uv_clip_tot);
                }
#endif

                if (pixel_bounds_array(uv_clip, &bounds_px, ibuf->x, ibuf->y, uv_clip_tot)) {
#if 0
                        project_paint_undo_tiles_init(
                                &bounds_px, ps->projImages + image_index, tmpibuf,
                                tile_width, threaded, ps->do_masking);
#endif
                        /* clip face and */

                        has_isect = 0;
                        for (y = bounds_px.ymin; y < bounds_px.ymax; y++) {
                                //uv[1] = (((float)y) + 0.5f) / (float)ibuf->y;
                                /* use pixel offset UV coords instead */
                                uv[1] = (float)y / ibuf_yf;

                                has_x_isect = 0;
                                for (x = bounds_px.xmin; x < bounds_px.xmax; x++) {
                                        //uv[0] = (((float)x) + 0.5f) / ibuf->x;
                                        /* use pixel offset UV coords instead */
                                        uv[0] = (float)x / ibuf_xf;

                                        /* Note about IsectPoly2Df_twoside, checking the face or uv flipping doesn't work,
                                         * could check the poly direction but better to do this */
                                        if ((do_backfacecull == true  && IsectPoly2Df(uv, uv_clip, uv_clip_tot)) ||
                                            (do_backfacecull == false && IsectPoly2Df_twoside(uv, uv_clip, uv_clip_tot)))
                                        {

                                                has_x_isect = has_isect = 1;

                                                if (is_ortho) screen_px_from_ortho(uv, v1coSS, v2coSS, v3coSS, uv1co, uv2co, uv3co, pixelScreenCo, w);
                                                else screen_px_from_persp(uv, v1coSS, v2coSS, v3coSS, uv1co, uv2co, uv3co, pixelScreenCo, w);

                                                /* a pity we need to get the worldspace pixel location here */
                                                if (do_clip || do_3d_mapping) {
                                                        interp_v3_v3v3v3(
                                                                wco,
                                                                ps->mvert_eval[lt_vtri[0]].co,
                                                                ps->mvert_eval[lt_vtri[1]].co,
                                                                ps->mvert_eval[lt_vtri[2]].co,
                                                                w);
                                                        if (do_clip && ED_view3d_clipping_test(ps->rv3d, wco, true)) {
                                                                /* Watch out that no code below this needs to run */
                                                                continue;
                                                        }
                                                }

                                                /* Is this UV visible from the view? - raytrace */
                                                /* project_paint_PickFace is less complex, use for testing */
                                                //if (project_paint_PickFace(ps, pixelScreenCo, w, &side) == tri_index) {
                                                if ((ps->do_occlude == false) ||
                                                    !project_bucket_point_occluded(ps, bucketFaceNodes, tri_index, pixelScreenCo))
                                                {
                                                        mask = project_paint_uvpixel_mask(ps, tri_index, w);

                                                        if (mask > 0.0f) {
                                                                BLI_linklist_prepend_arena(
                                                                        bucketPixelNodes,
                                                                        project_paint_uvpixel_init(
                                                                                ps, arena, &tinf, x, y, mask, tri_index,
                                                                                pixelScreenCo, wco, w),
                                                                        arena);
                                                        }
                                                }

                                        }
//#if 0
                                        else if (has_x_isect) {
                                                /* assuming the face is not a bow-tie - we know we cant intersect again on the X */
                                                break;
                                        }
//#endif
                                }


#if 0           /* TODO - investigate why this dosnt work sometimes! it should! */
                                /* no intersection for this entire row,
                                 * after some intersection above means we can quit now */
                                if (has_x_isect == 0 && has_isect) {
                                        break;
                                }
#endif
                        }
                }
        }


#ifndef PROJ_DEBUG_NOSEAMBLEED
        if (ps->seam_bleed_px > 0.0f) {
                int face_seam_flag;

                if (threaded) {
                        /* Other threads could be modifying these vars. */
                        BLI_thread_lock(LOCK_CUSTOM1);
                }

                face_seam_flag = ps->faceSeamFlags[tri_index];

                /* are any of our edges un-initialized? */
                if ((face_seam_flag & (PROJ_FACE_SEAM1 | PROJ_FACE_NOSEAM1)) == 0 ||
                    (face_seam_flag & (PROJ_FACE_SEAM2 | PROJ_FACE_NOSEAM2)) == 0 ||
                    (face_seam_flag & (PROJ_FACE_SEAM3 | PROJ_FACE_NOSEAM3)) == 0)
                {
                        project_face_seams_init(ps, tri_index);
                        face_seam_flag = ps->faceSeamFlags[tri_index];
                        //printf("seams - %d %d %d %d\n", flag&PROJ_FACE_SEAM1, flag&PROJ_FACE_SEAM2, flag&PROJ_FACE_SEAM3);
                }

                if ((face_seam_flag & (PROJ_FACE_SEAM1 | PROJ_FACE_SEAM2 | PROJ_FACE_SEAM3)) == 0) {

                        if (threaded) {
                                /* Other threads could be modifying these vars. */
                                BLI_thread_unlock(LOCK_CUSTOM1);
                        }

                }
                else {
                        /* we have a seam - deal with it! */

                        /* Now create new UV's for the seam face */
                        float (*outset_uv)[2] = ps->faceSeamUVs[tri_index];
                        /* inset face coords.  NOTE!!! ScreenSace for ortho, Worldspace in perspective view */
                        float insetCos[3][3];

                        /* vertex screenspace coords */
                        const float *vCoSS[3];

                        /* Store the screenspace coords of the face,
                         * clipped by the bucket's screen aligned rectangle. */
                        float bucket_clip_edges[2][2];
                        float edge_verts_inset_clip[2][3];
                        /* face edge pairs - loop throuh these:
                         * ((0,1), (1,2), (2,3), (3,0)) or ((0,1), (1,2), (2,0)) for a tri */
                        int fidx1, fidx2;

                        float seam_subsection[4][2];
                        float fac1, fac2;

                        if (outset_uv[0][0] == FLT_MAX) /* first time initialize */
                                uv_image_outset(
                                        lt_uv_pxoffset, outset_uv, ps->seam_bleed_px,
                                        ibuf->x, ibuf->y, (ps->faceWindingFlags[tri_index] & PROJ_FACE_WINDING_CW) == 0);

                        /* ps->faceSeamUVs cant be modified when threading, now this is done we can unlock. */
                        if (threaded) {
                                /* Other threads could be modifying these vars */
                                BLI_thread_unlock(LOCK_CUSTOM1);
                        }

                        vCoSS[0] = ps->screenCoords[lt_vtri[0]];
                        vCoSS[1] = ps->screenCoords[lt_vtri[1]];
                        vCoSS[2] = ps->screenCoords[lt_vtri[2]];

                        /* PROJ_FACE_SCALE_SEAM must be slightly less then 1.0f */
                        if (is_ortho) {
                                scale_tri(insetCos, vCoSS, PROJ_FACE_SCALE_SEAM);
                        }
                        else {
                                scale_tri(insetCos, vCo, PROJ_FACE_SCALE_SEAM);
                        }

                        for (fidx1 = 0; fidx1 < 3; fidx1++) {
                                /* next fidx in the face (0,1,2) -> (1,2,0) */
                                fidx2 = (fidx1 == 2) ? 0 : fidx1 + 1;

                                if ((face_seam_flag & (1 << fidx1)) && /* 1<<fidx1 -> PROJ_FACE_SEAM# */
                                    line_clip_rect2f(clip_rect, bucket_bounds, vCoSS[fidx1], vCoSS[fidx2], bucket_clip_edges[0], bucket_clip_edges[1]))
                                {
                                        /* Avoid div by zero. */
                                        if (len_squared_v2v2(vCoSS[fidx1], vCoSS[fidx2]) > FLT_EPSILON) {

                                                if (is_ortho) {
                                                        fac1 = line_point_factor_v2(bucket_clip_edges[0], vCoSS[fidx1], vCoSS[fidx2]);
                                                        fac2 = line_point_factor_v2(bucket_clip_edges[1], vCoSS[fidx1], vCoSS[fidx2]);
                                                }
                                                else {
                                                        fac1 = screen_px_line_point_factor_v2_persp(ps, bucket_clip_edges[0], vCo[fidx1], vCo[fidx2]);
                                                        fac2 = screen_px_line_point_factor_v2_persp(ps, bucket_clip_edges[1], vCo[fidx1], vCo[fidx2]);
                                                }

                                                interp_v2_v2v2(seam_subsection[0], lt_uv_pxoffset[fidx1], lt_uv_pxoffset[fidx2], fac1);
                                                interp_v2_v2v2(seam_subsection[1], lt_uv_pxoffset[fidx1], lt_uv_pxoffset[fidx2], fac2);

                                                interp_v2_v2v2(seam_subsection[2], outset_uv[fidx1], outset_uv[fidx2], fac2);
                                                interp_v2_v2v2(seam_subsection[3], outset_uv[fidx1], outset_uv[fidx2], fac1);

                                                /* if the bucket_clip_edges values Z values was kept we could avoid this
                                                 * Inset needs to be added so occlusion tests wont hit adjacent faces */
                                                interp_v3_v3v3(edge_verts_inset_clip[0], insetCos[fidx1], insetCos[fidx2], fac1);
                                                interp_v3_v3v3(edge_verts_inset_clip[1], insetCos[fidx1], insetCos[fidx2], fac2);


                                                if (pixel_bounds_uv(seam_subsection, &bounds_px, ibuf->x, ibuf->y)) {
                                                        /* bounds between the seam rect and the uvspace bucket pixels */

                                                        has_isect = 0;
                                                        for (y = bounds_px.ymin; y < bounds_px.ymax; y++) {
                                                                // uv[1] = (((float)y) + 0.5f) / (float)ibuf->y;
                                                                /* use offset uvs instead */
                                                                uv[1] = (float)y / ibuf_yf;

                                                                has_x_isect = 0;
                                                                for (x = bounds_px.xmin; x < bounds_px.xmax; x++) {
                                                                        //uv[0] = (((float)x) + 0.5f) / (float)ibuf->x;
                                                                        /* use offset uvs instead */
                                                                        uv[0] = (float)x / ibuf_xf;

                                                                        /* test we're inside uvspace bucket and triangle bounds */
                                                                        if (isect_point_quad_v2(uv, UNPACK4(seam_subsection))) {
                                                                                float fac;

                                                                                /* We need to find the closest point along the face edge,
                                                                                 * getting the screen_px_from_*** wont work because our
                                                                                 * actual location is not relevant, since we are outside
                                                                                 * the face, Use VecLerpf to find our location on the side
                                                                                 * of the face's UV */
#if 0
                                                                                if (is_ortho) screen_px_from_ortho(ps, uv, v1co, v2co, v3co, uv1co, uv2co, uv3co, pixelScreenCo);
                                                                                else          screen_px_from_persp(ps, uv, v1co, v2co, v3co, uv1co, uv2co, uv3co, pixelScreenCo);
#endif

                                                                                /* Since this is a seam we need to work out where on
                                                                                 * the line this pixel is */
                                                                                //fac = line_point_factor_v2(uv, uv_seam_quad[0], uv_seam_quad[1]);
                                                                                fac = resolve_quad_u_v2(uv, UNPACK4(seam_subsection));
                                                                                interp_v3_v3v3(pixelScreenCo, edge_verts_inset_clip[0], edge_verts_inset_clip[1], fac);

                                                                                if (!is_ortho) {
                                                                                        pixelScreenCo[3] = 1.0f;
                                                                                        /* cast because of const */
                                                                                        mul_m4_v4((float(*)[4])ps->projectMat, pixelScreenCo);
                                                                                        pixelScreenCo[0] = (float)(ps->winx * 0.5f) + (ps->winx * 0.5f) * pixelScreenCo[0] / pixelScreenCo[3];
                                                                                        pixelScreenCo[1] = (float)(ps->winy * 0.5f) + (ps->winy * 0.5f) * pixelScreenCo[1] / pixelScreenCo[3];
                                                                                        /* Use the depth for bucket point occlusion */
                                                                                        pixelScreenCo[2] = pixelScreenCo[2] / pixelScreenCo[3];
                                                                                }

                                                                                if ((ps->do_occlude == false) ||
                                                                                    !project_bucket_point_occluded(ps, bucketFaceNodes, tri_index, pixelScreenCo))
                                                                                {
                                                                                        /* Only bother calculating the weights if we intersect */
                                                                                        if (ps->do_mask_normal || ps->poly_to_loop_uv_clone) {
                                                                                                const float uv_fac = fac1 + (fac * (fac2 - fac1));
#if 0
                                                                                                /* get the UV on the line since we want to copy the
                                                                                                 * pixels from there for bleeding */
                                                                                                float uv_close[2];
                                                                                                interp_v2_v2v2(uv_close, lt_uv_pxoffset[fidx1], lt_uv_pxoffset[fidx2], uv_fac);
                                                                                                barycentric_weights_v2(lt_uv_pxoffset[0], lt_uv_pxoffset[1], lt_uv_pxoffset[2], uv_close, w);
#else

                                                                                                /* Cheat, we know where we are along the edge
                                                                                                 * so work out the weights from that */
                                                                                                w[0] = w[1] = w[2] = 0.0;
                                                                                                w[fidx1] = 1.0f - uv_fac;
                                                                                                w[fidx2] = uv_fac;
#endif
                                                                                        }

                                                                                        /* a pity we need to get the worldspace
                                                                                         * pixel location here */
                                                                                        if (do_clip || do_3d_mapping) {
                                                                                                interp_v3_v3v3v3(wco, vCo[0], vCo[1], vCo[2], w);

                                                                                                if (do_clip && ED_view3d_clipping_test(ps->rv3d, wco, true)) {
                                                                                                        /* Watch out that no code below
                                                                                                         * this needs to run */
                                                                                                        continue;
                                                                                                }
                                                                                        }