[Bf-blender-cvs] [70424195a8a] blender-v3.0-release: Cycles: Fix possible access to non-initialized light sample in volume

[Sergey Sharybin]

Commit: 70424195a8a68f5d08f91b5947008825af7b4ee8
Author: Sergey Sharybin
Date:   Tue Nov 23 15:11:00 2021 +0100
Branches: blender-v3.0-release
https://developer.blender.org/rB70424195a8a68f5d08f91b5947008825af7b4ee8

Cycles: Fix possible access to non-initialized light sample in volume

Happened in barbershop file where number of bounces to the light was
reached.

Differential Revision: https://developer.blender.org/D13336

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

M	intern/cycles/kernel/integrator/shade_volume.h
M	intern/cycles/kernel/light/light.h

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

diff --git a/intern/cycles/kernel/integrator/shade_volume.h b/intern/cycles/kernel/integrator/shade_volume.h
index 3a2bf04d533..cc47557d580 100644
--- a/intern/cycles/kernel/integrator/shade_volume.h
+++ b/intern/cycles/kernel/integrator/shade_volume.h
@@ -703,8 +703,10 @@ ccl_device_forceinline bool integrate_volume_sample_light(
   float light_u, light_v;
   path_state_rng_2D(kg, rng_state, PRNG_LIGHT_U, &light_u, &light_v);
 
-  light_distribution_sample_from_volume_segment(
-      kg, light_u, light_v, sd->time, sd->P, bounce, path_flag, ls);
+  if (!light_distribution_sample_from_volume_segment(
+          kg, light_u, light_v, sd->time, sd->P, bounce, path_flag, ls)) {
+    return false;
+  }
 
   if (ls->shader & SHADER_EXCLUDE_SCATTER) {
     return false;
diff --git a/intern/cycles/kernel/light/light.h b/intern/cycles/kernel/light/light.h
index 2e7f862a715..97dca936552 100644
--- a/intern/cycles/kernel/light/light.h
+++ b/intern/cycles/kernel/light/light.h
@@ -73,7 +73,7 @@ ccl_device_inline bool light_sample(KernelGlobals kg,
     ls->P = zero_float3();
     ls->Ng = zero_float3();
     ls->D = zero_float3();
-    ls->pdf = true;
+    ls->pdf = 1.0f;
     ls->t = FLT_MAX;
     return true;
   }
@@ -131,7 +131,7 @@ ccl_device_inline bool light_sample(KernelGlobals kg,
         float3 dir = make_float3(klight->spot.dir[0], klight->spot.dir[1], klight->spot.dir[2]);
         ls->eval_fac *= spot_light_attenuation(
             dir, klight->spot.spot_angle, klight->spot.spot_smooth, ls->Ng);
-        if (ls->eval_fac == 0.0f) {
+        if (!in_volume_segment && ls->eval_fac == 0.0f) {
           return false;
         }
       }
@@ -170,7 +170,7 @@ ccl_device_inline bool light_sample(KernelGlobals kg,
         float3 sample_axisu = axisu;
         float3 sample_axisv = axisv;
 
-        if (klight->area.tan_spread > 0.0f) {
+        if (!in_volume_segment && klight->area.tan_spread > 0.0f) {
           if (!light_spread_clamp_area_light(
                   P, Ng, &ls->P, &sample_axisu, &sample_axisv, klight->area.tan_spread)) {
             return false;
@@ -203,7 +203,7 @@ ccl_device_inline bool light_sample(KernelGlobals kg,
 
   ls->pdf *= kernel_data.integrator.pdf_lights;
 
-  return (ls->pdf > 0.0f);
+  return in_volume_segment || (ls->pdf > 0.0f);
 }
 
 ccl_device bool lights_intersect(KernelGlobals kg,