[Bf-blender-cvs] [3f1e3d2dfa6] soc-2022-many-lights-sampling: Cycles: handle case where light tree importance is 0

[Jeffrey Liu]

Commit: 3f1e3d2dfa61e784c978a1d7931c1bec8be1e9ff
Author: Jeffrey Liu
Date:   Wed Jun 15 10:24:20 2022 -0400
Branches: soc-2022-many-lights-sampling
https://developer.blender.org/rB3f1e3d2dfa61e784c978a1d7931c1bec8be1e9ff

Cycles: handle case where light tree importance is 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 c5f1f52f05e..cf3ffa18497 100644
--- a/intern/cycles/kernel/light/light_tree.h
+++ b/intern/cycles/kernel/light/light_tree.h
@@ -154,8 +154,13 @@ ccl_device bool light_tree_sample(KernelGlobals kg,
     }
   }
 
-  /* Once we're at a leaf node, we can sample from the cluster of primitives inside.
-   * Right now, this is done by incrementing the CDF by the PDF.
+  /* Special case where there's only a single light. */
+  if (knode->num_prims == 1) {
+    return light_sample<in_volume_segment>(
+        kg, -knode->child_index, randu, randv, P, path_flag, ls);
+  }
+
+  /* Right now, sampling is done by incrementing the CDF by the PDF.
    * However, we first need to calculate the total importance so that we can normalize the CDF. */
   float total_emitter_importance = 0.0f;
   for (int i = 0; i < knode->num_prims; i++) {
@@ -163,12 +168,11 @@ ccl_device bool light_tree_sample(KernelGlobals kg,
     total_emitter_importance += light_tree_emitter_importance(kg, P, N, prim_index);
   }
 
-  /* to-do: need to handle a case when total importance is 0.*/
+  /* to-do: need to handle a case when total importance is 0. */
   if (total_emitter_importance == 0.0f) {
-
+    return false;
   }
 
-
   /* Once we have the total importance, we can normalize the CDF and sample it. */
   const float inv_total_importance = 1 / total_emitter_importance;
   float emitter_cdf = 0.0f;