Cycles: Fix wrong termination criteria in intersect_all functions

It was possible to miss bounces termination criteria in this functions,
mainly when max_hits was set to 0.

Made the check more robust in traversal functions (which should not
affect performance, it's an operation of same complexity AFAIK).

Also avoid doing ray-scene intersection from shadow_blocked when
limit of transparent bounces was already reached.

5 files changed, 12 insertions, 7 deletions

diff --git a/intern/cycles/kernel/bvh/bvh_shadow_all.h b/intern/cycles/kernel/bvh/bvh_shadow_all.h
index 1869457f0c3..b27afaa9869 100644
--- a/intern/cycles/kernel/bvh/bvh_shadow_all.h
+++ b/intern/cycles/kernel/bvh/bvh_shadow_all.h
@@ -283,7 +283,7 @@ ccl_device bool BVH_FUNCTION_FULL_NAME(BVH)(KernelGlobals *kg,
 								return true;
 							}
 							/* if maximum number of hits reached, block all light */
-							else if(*num_hits == max_hits) {
+							else if(*num_hits >= max_hits) {
 								return true;
 							}
 
diff --git a/intern/cycles/kernel/bvh/bvh_volume_all.h b/intern/cycles/kernel/bvh/bvh_volume_all.h
index b5405e8e57b..d7f6bf86c71 100644
--- a/intern/cycles/kernel/bvh/bvh_volume_all.h
+++ b/intern/cycles/kernel/bvh/bvh_volume_all.h
@@ -206,7 +206,7 @@ ccl_device uint BVH_FUNCTION_FULL_NAME(BVH)(KernelGlobals *kg,
 #if BVH_FEATURE(BVH_INSTANCING)
 									num_hits_in_instance++;
 #endif
-									if(num_hits == max_hits) {
+									if(num_hits >= max_hits) {
 #if BVH_FEATURE(BVH_INSTANCING)
 #  if BVH_FEATURE(BVH_MOTION)
 										float t_fac = 1.0f / len(transform_direction(&ob_itfm, dir));
@@ -252,7 +252,7 @@ ccl_device uint BVH_FUNCTION_FULL_NAME(BVH)(KernelGlobals *kg,
 #  if BVH_FEATURE(BVH_INSTANCING)
 									num_hits_in_instance++;
 #  endif
-									if(num_hits == max_hits) {
+									if(num_hits >= max_hits) {
 #  if BVH_FEATURE(BVH_INSTANCING)
 #    if BVH_FEATURE(BVH_MOTION)
 										float t_fac = 1.0f / len(transform_direction(&ob_itfm, dir));
diff --git a/intern/cycles/kernel/bvh/qbvh_shadow_all.h b/intern/cycles/kernel/bvh/qbvh_shadow_all.h
index 34753ff067d..eb98eaf7455 100644
--- a/intern/cycles/kernel/bvh/qbvh_shadow_all.h
+++ b/intern/cycles/kernel/bvh/qbvh_shadow_all.h
@@ -366,7 +366,7 @@ ccl_device bool BVH_FUNCTION_FULL_NAME(QBVH)(KernelGlobals *kg,
 								return true;
 							}
 							/* if maximum number of hits reached, block all light */
-							else if(*num_hits == max_hits) {
+							else if(*num_hits >= max_hits) {
 								return true;
 							}
 
diff --git a/intern/cycles/kernel/bvh/qbvh_volume_all.h b/intern/cycles/kernel/bvh/qbvh_volume_all.h
index a877e5bb341..90cad9d91c0 100644
--- a/intern/cycles/kernel/bvh/qbvh_volume_all.h
+++ b/intern/cycles/kernel/bvh/qbvh_volume_all.h
@@ -273,7 +273,7 @@ ccl_device uint BVH_FUNCTION_FULL_NAME(QBVH)(KernelGlobals *kg,
 #if BVH_FEATURE(BVH_INSTANCING)
 									num_hits_in_instance++;
 #endif
-									if(num_hits == max_hits) {
+									if(num_hits >= max_hits) {
 #if BVH_FEATURE(BVH_INSTANCING)
 #  if BVH_FEATURE(BVH_MOTION)
 										float t_fac = 1.0f / len(transform_direction(&ob_itfm, dir));
@@ -312,7 +312,7 @@ ccl_device uint BVH_FUNCTION_FULL_NAME(QBVH)(KernelGlobals *kg,
 #  if BVH_FEATURE(BVH_INSTANCING)
 									num_hits_in_instance++;
 #  endif
-									if(num_hits == max_hits) {
+									if(num_hits >= max_hits) {
 #  if BVH_FEATURE(BVH_INSTANCING)
 #    if BVH_FEATURE(BVH_MOTION)
 										float t_fac = 1.0f / len(transform_direction(&ob_itfm, dir));
diff --git a/intern/cycles/kernel/kernel_shadow.h b/intern/cycles/kernel/kernel_shadow.h
index db2fc84834a..d1576754d2e 100644
--- a/intern/cycles/kernel/kernel_shadow.h
+++ b/intern/cycles/kernel/kernel_shadow.h
@@ -75,7 +75,12 @@ ccl_device_inline bool shadow_blocked(KernelGlobals *kg, ShaderData *shadow_sd,
 		}
 
 		uint num_hits;
-		blocked = scene_intersect_shadow_all(kg, ray, hits, max_hits, &num_hits);
+		if(max_hits == 0) {
+			blocked = true;
+			num_hits = 0;
+		} else {
+			blocked = scene_intersect_shadow_all(kg, ray, hits, max_hits, &num_hits);
+		}
 
 		/* if no opaque surface found but we did find transparent hits, shade them */
 		if(!blocked && num_hits > 0) {