[Bf-blender-cvs] [702a2d075e1] soc-2022-many-lights-sampling: Fix: light tree has artifacts with many lights

[Jeffrey Liu]

Commit: 702a2d075e141f6c5dfe6ea6a4e29a6a6e8c8d7a
Author: Jeffrey Liu
Date:   Fri Aug 5 00:06:19 2022 -0400
Branches: soc-2022-many-lights-sampling
https://developer.blender.org/rB702a2d075e141f6c5dfe6ea6a4e29a6a6e8c8d7a

Fix: light tree has artifacts with many lights

This fix resolves artifacts when there are many lights. This is because
it was sampling lights when the total importance was 0.

===================================================================

M	intern/cycles/kernel/light/light_tree.h

===================================================================

diff --git a/intern/cycles/kernel/light/light_tree.h b/intern/cycles/kernel/light/light_tree.h
index d44ed34cb15..c15e6ebed37 100644
--- a/intern/cycles/kernel/light/light_tree.h
+++ b/intern/cycles/kernel/light/light_tree.h
@@ -372,6 +372,12 @@ ccl_device bool light_tree_sample(KernelGlobals kg,
 
     const float left_importance = light_tree_cluster_importance(kg, P, N, left);
     const float right_importance = light_tree_cluster_importance(kg, P, N, right);
+    const float total_importance = left_importance + right_importance;
+
+    if (total_importance == 0.0f) {
+      stack_index--;
+      continue;
+    }
     float left_probability = left_importance / (left_importance + right_importance);
 
     if (*randu < left_probability) {