Cycles: Crash fix for random walk SSS with Embree.

1 files changed, 22 insertions, 16 deletions

diff --git a/intern/cycles/bvh/bvh_embree.cpp b/intern/cycles/bvh/bvh_embree.cpp
index d12a0c137ea..42d2e66017c 100644
--- a/intern/cycles/bvh/bvh_embree.cpp
+++ b/intern/cycles/bvh/bvh_embree.cpp
@@ -168,26 +168,32 @@ static void rtc_filter_occluded_func(const RTCFilterFunctionNArguments *args)
         }
       }
 
-      ++ctx->ss_isect->num_hits;
-      int hit_idx;
+      int hit_idx = 0;
 
-      if (ctx->ss_isect->num_hits <= ctx->max_hits) {
-        hit_idx = ctx->ss_isect->num_hits - 1;
-      }
-      else {
-        /* reservoir sampling: if we are at the maximum number of
-         * hits, randomly replace element or skip it */
-        hit_idx = lcg_step_uint(ctx->lcg_state) % ctx->ss_isect->num_hits;
+      if (ctx->lcg_state) {
 
-        if (hit_idx >= ctx->max_hits) {
-          /* This tells Embree to continue tracing. */
-          *args->valid = 0;
-          break;
+        ++ctx->ss_isect->num_hits;
+        if (ctx->ss_isect->num_hits <= ctx->max_hits) {
+          hit_idx = ctx->ss_isect->num_hits - 1;
+        }
+        else {
+          /* reservoir sampling: if we are at the maximum number of
+           * hits, randomly replace element or skip it */
+          hit_idx = lcg_step_uint(ctx->lcg_state) % ctx->ss_isect->num_hits;
+
+          if (hit_idx >= ctx->max_hits) {
+            /* This tells Embree to continue tracing. */
+            *args->valid = 0;
+            break;
+          }
         }
       }
-      /* record intersection */
-      kernel_embree_convert_local_hit(
-          kg, ray, hit, &ctx->ss_isect->hits[hit_idx], ctx->sss_object_id);
+      else {
+        ctx->ss_isect->num_hits = 1;
+	  }
+        /* record intersection */
+        kernel_embree_convert_local_hit(
+            kg, ray, hit, &ctx->ss_isect->hits[hit_idx], ctx->sss_object_id);
       ctx->ss_isect->Ng[hit_idx].x = hit->Ng_x;
       ctx->ss_isect->Ng[hit_idx].y = hit->Ng_y;
       ctx->ss_isect->Ng[hit_idx].z = hit->Ng_z;