Fix T43562: Cycles gets stuck with camera in volume in certain setup
authorSergey Sharybin <sergey.vfx@gmail.com>
Thu, 5 Feb 2015 11:06:22 +0000 (16:06 +0500)
committerSergey Sharybin <sergey.vfx@gmail.com>
Thu, 5 Feb 2015 11:10:50 +0000 (16:10 +0500)
The issue was caused by the way how we shoot the ray to see which rays we're
inside which might start bouncing back-n-forth between two close to parallel
intersecting faces.

Real solution would be to record all the intersections when shooting the ray,
but it's kinda tricky on GPU because of needed sorting and uncertainty of
how huge intersection array should be.

For now we'll just limit number of steps in the check so in worst case we'll
have some samples not being correct which will be compensated with further
sampling. Shouldn't be an issue since probability of such a lock is quite
small actually.

intern/cycles/kernel/kernel_path.h
intern/cycles/kernel/kernel_volume.h

index 8eb6866068eeb5cabe0edc296510ef6800f884c1..a1012cf2b727453225772b36ddb93f26ea61c3bd 100644 (file)
@@ -373,8 +373,9 @@ ccl_device void kernel_path_subsurface_update_volume_stack(KernelGlobals *kg,
 
        Ray volume_ray = *ray;
        Intersection isect;
-
-       while(scene_intersect_volume(kg, &volume_ray, &isect))
+       int step = 0;
+       while(step < VOLUME_STACK_SIZE &&
+             scene_intersect_volume(kg, &volume_ray, &isect))
        {
                ShaderData sd;
                shader_setup_from_ray(kg, &sd, &isect, &volume_ray, 0, 0);
@@ -383,6 +384,7 @@ ccl_device void kernel_path_subsurface_update_volume_stack(KernelGlobals *kg,
                /* Move ray forward. */
                volume_ray.P = ray_offset(sd.P, -sd.Ng);
                volume_ray.t -= sd.ray_length;
+               ++step;
        }
 }
 #endif
index b2181952aeb6b42ffcc1d10f6e086a1a8dc31ac3..9d6c233f5b2a565c29fd611a561f7adc74ab47c4 100644 (file)
@@ -980,9 +980,11 @@ ccl_device void kernel_volume_stack_init(KernelGlobals *kg,
 
        int stack_index = 0, enclosed_index = 0;
        int enclosed_volumes[VOLUME_STACK_SIZE];
+       int step = 0;
 
        while(stack_index < VOLUME_STACK_SIZE - 1 &&
-             enclosed_index < VOLUME_STACK_SIZE - 1)
+             enclosed_index < VOLUME_STACK_SIZE - 1 &&
+             step < 2 * VOLUME_STACK_SIZE)
        {
                Intersection isect;
                if(!scene_intersect_volume(kg, &volume_ray, &isect)) {
@@ -1017,6 +1019,7 @@ ccl_device void kernel_volume_stack_init(KernelGlobals *kg,
 
                /* Move ray forward. */
                volume_ray.P = ray_offset(sd.P, -sd.Ng);
+               ++step;
        }
        /* stack_index of 0 means quick checks outside of the kernel gave false
         * positive, nothing to worry about, just we've wasted quite a few of