Fix T66296: Black artefacts on materials with refraction on CPU

The issue was in the optimization code path for opaque shadow rays
which was wrongly considering all primitives in the node to have
same visibility flags.

1 files changed, 27 insertions, 18 deletions

diff --git a/intern/cycles/kernel/geom/geom_triangle_intersect.h b/intern/cycles/kernel/geom/geom_triangle_intersect.h
index 9c6fd498a80..68075199402 100644
--- a/intern/cycles/kernel/geom/geom_triangle_intersect.h
+++ b/intern/cycles/kernel/geom/geom_triangle_intersect.h
@@ -232,27 +232,36 @@ ccl_device_inline int ray_triangle_intersect8(KernelGlobals *kg,
     mask_final_256 = _mm256_andnot_si256(mask0, mask_final_256);  //(~mask_minmaxUVW_pos) &(~mask)
     mask_final_256 = _mm256_andnot_si256(
         maskden256, mask_final_256);  //(~mask_minmaxUVW_pos) &(~mask) & (~maskden)
-    unsigned char mask_final = _mm256_movemask_ps(_mm256_castsi256_ps(mask_final_256));
+    int mask_final = _mm256_movemask_ps(_mm256_castsi256_ps(mask_final_256));
     if ((mask_final & prim_num_mask) == 0) {
       return false;
     }
-    const int i = __bsf(mask_final);
-    __m256 inv_den_256 = _mm256_rcp_ps(den_256);
-    U_256 = _mm256_mul_ps(U_256, inv_den_256);
-    V_256 = _mm256_mul_ps(V_256, inv_den_256);
-    T_256 = _mm256_mul_ps(T_256, inv_den_256);
-    _mm256_store_ps(U8, U_256);
-    _mm256_store_ps(V8, V_256);
-    _mm256_store_ps(T8, T_256);
-    /* NOTE: Here we assume visibility for all triangles in the node is
-     * the same. */
-    (*isect)->u = U8[i];
-    (*isect)->v = V8[i];
-    (*isect)->t = T8[i];
-    (*isect)->prim = (prim_addr + i);
-    (*isect)->object = object;
-    (*isect)->type = PRIMITIVE_TRIANGLE;
-    return true;
+    while (mask_final != 0) {
+      const int i = __bscf(mask_final);
+      if (i >= prim_num) {
+        return false;
+      }
+#  ifdef __VISIBILITY_FLAG__
+      if ((kernel_tex_fetch(__prim_visibility, (prim_addr + i)) & visibility) == 0) {
+        continue;
+      }
+#  endif
+      __m256 inv_den_256 = _mm256_rcp_ps(den_256);
+      U_256 = _mm256_mul_ps(U_256, inv_den_256);
+      V_256 = _mm256_mul_ps(V_256, inv_den_256);
+      T_256 = _mm256_mul_ps(T_256, inv_den_256);
+      _mm256_store_ps(U8, U_256);
+      _mm256_store_ps(V8, V_256);
+      _mm256_store_ps(T8, T_256);
+      (*isect)->u = U8[i];
+      (*isect)->v = V8[i];
+      (*isect)->t = T8[i];
+      (*isect)->prim = (prim_addr + i);
+      (*isect)->object = object;
+      (*isect)->type = PRIMITIVE_TRIANGLE;
+      return true;
+    }
+    return false;
   }
   else {
     _mm256_store_ps(den8, den_256);