StudioLight: Use texel size as input size
authorJeroen Bakker <j.bakker@atmind.nl>
Tue, 12 Jun 2018 14:18:07 +0000 (16:18 +0200)
committerJeroen Bakker <j.bakker@atmind.nl>
Tue, 12 Jun 2018 14:18:50 +0000 (16:18 +0200)
Bettter light distribution for diffuse shading

source/blender/blenkernel/intern/studiolight.c

index acc6fdcfb819a8e2645e1b4f10397d3707b2d52c..a90ae6d5c6f11cb6445eb7d85cd749c71ce5fa8f 100644 (file)
@@ -347,8 +347,30 @@ static void studiolight_calculate_diffuse_light(StudioLight *sl)
        sl->flag |= STUDIOLIGHT_DIFFUSE_LIGHT_CALCULATED;
 }
 
+static float area_element(float x, float y )
+{
+       return atan2f(x * y, sqrt(x * x + y * y + 1));
+}
+
+static float texel_coord_solid_angle(float a_U, float a_V, int a_Size)
+{
+       //scale up to [-1, 1] range (inclusive), offset by 0.5 to point to texel center.
+       float u = (2.0f * ((float)a_U + 0.5f) / (float)a_Size ) - 1.0f;
+       float v = (2.0f * ((float)a_V + 0.5f) / (float)a_Size ) - 1.0f;
+
+       float resolution_inv = 1.0f / a_Size;
+
+       // U and V are the -1..1 texture coordinate on the current face.
+       // Get projected area for this texel
+       float x0 = u - resolution_inv;
+       float y0 = v - resolution_inv;
+       float x1 = u + resolution_inv;
+       float y1 = v + resolution_inv;
+       return area_element(x0, y0) - area_element(x0, y1) - area_element(x1, y0) + area_element(x1, y1);
+}
+
 BLI_INLINE void studiolight_evaluate_specular_radiance_buffer(
-        ImBuf *radiance_buffer, const float specular, const float normal[3], float color[3], int *hits,
+        ImBuf *radiance_buffer, const float normal[3], float color[3], 
         int xoffset, int yoffset, int zoffset, float zvalue)
 {
        if (radiance_buffer == NULL) {
@@ -360,13 +382,14 @@ BLI_INLINE void studiolight_evaluate_specular_radiance_buffer(
        for (int y = 0; y < STUDIOLIGHT_RADIANCE_CUBEMAP_SIZE; y ++) {
                for (int x = 0; x < STUDIOLIGHT_RADIANCE_CUBEMAP_SIZE; x ++) {
                        // calculate light direction;
+                       float u = (x / (float)STUDIOLIGHT_RADIANCE_CUBEMAP_SIZE) - 0.5f;
+                       float v = (y / (float)STUDIOLIGHT_RADIANCE_CUBEMAP_SIZE) - 0.5f;
                        direction[zoffset] = zvalue;
-                       direction[xoffset] = (x / (float)STUDIOLIGHT_RADIANCE_CUBEMAP_SIZE) - 0.5f;
-                       direction[yoffset] = (y / (float)STUDIOLIGHT_RADIANCE_CUBEMAP_SIZE) - 0.5f;
+                       direction[xoffset] = u;
+                       direction[yoffset] = v;
                        normalize_v3(direction);
-                       angle = pow(fmax(0.0f, dot_v3v3(direction, normal)), specular);
+                       angle = fmax(0.0f, dot_v3v3(direction, normal)) * texel_coord_solid_angle(x, y, STUDIOLIGHT_RADIANCE_CUBEMAP_SIZE);
                        madd_v3_v3fl(color, radiance_color, angle);
-                       (*hits) ++;
                        radiance_color += 4;
                }
        }
@@ -375,30 +398,28 @@ BLI_INLINE void studiolight_evaluate_specular_radiance_buffer(
 
 static void studiolight_calculate_specular_irradiance(StudioLight *sl, float color[3], const float normal[3])
 {
-       const float specular = 1.0f;
-       int hits = 0;
        copy_v3_fl(color, 0.0f);
 
        /* back */
        studiolight_evaluate_specular_radiance_buffer(
-               sl->radiance_cubemap_buffers[STUDIOLIGHT_Y_POS], specular, normal, color, &hits, 0, 2, 1, 0.5);
+               sl->radiance_cubemap_buffers[STUDIOLIGHT_Y_POS], normal, color, 0, 2, 1, 0.5);
        /* front */
        studiolight_evaluate_specular_radiance_buffer(
-               sl->radiance_cubemap_buffers[STUDIOLIGHT_Y_NEG], specular, normal, color, &hits, 0, 2, 1, -0.5);
+               sl->radiance_cubemap_buffers[STUDIOLIGHT_Y_NEG], normal, color, 0, 2, 1, -0.5);
 
        /* left */
        studiolight_evaluate_specular_radiance_buffer(
-               sl->radiance_cubemap_buffers[STUDIOLIGHT_X_POS], specular, normal, color, &hits, 1, 2, 0, 0.5);
+               sl->radiance_cubemap_buffers[STUDIOLIGHT_X_POS], normal, color, 1, 2, 0, 0.5);
        /* right */
        studiolight_evaluate_specular_radiance_buffer(
-               sl->radiance_cubemap_buffers[STUDIOLIGHT_X_NEG], specular, normal, color, &hits, 1, 2, 0, -0.5);
+               sl->radiance_cubemap_buffers[STUDIOLIGHT_X_NEG], normal, color, 1, 2, 0, -0.5);
 
        /* top */
        studiolight_evaluate_specular_radiance_buffer(
-               sl->radiance_cubemap_buffers[STUDIOLIGHT_Z_POS], specular, normal, color, &hits, 0, 1, 2, 0.5);
+               sl->radiance_cubemap_buffers[STUDIOLIGHT_Z_POS], normal, color, 0, 1, 2, 0.5);
        /* bottom */
        studiolight_evaluate_specular_radiance_buffer(
-               sl->radiance_cubemap_buffers[STUDIOLIGHT_Z_NEG], specular, normal, color, &hits, 0, 1, 2, -0.5);
+               sl->radiance_cubemap_buffers[STUDIOLIGHT_Z_NEG], normal, color, 0, 1, 2, -0.5);
 
        mul_v3_fl(color, 1.0/ M_PI);
 }