[Bf-blender-cvs] [7d291fae0f5] temp-studio-sprite-fright-cycles: Cycles: Ensure finite displacement and background evaluation

[Sergey Sharybin]

Commit: 7d291fae0f5ba6e301c4aa9c4a9492f94fd0f175
Author: Sergey Sharybin
Date:   Wed Sep 29 14:31:18 2021 +0200
Branches: temp-studio-sprite-fright-cycles
https://developer.blender.org/rB7d291fae0f5ba6e301c4aa9c4a9492f94fd0f175

Cycles: Ensure finite displacement and background evaluation

Avoids possible numerical issues in the path tracing kernel, which
is most important for displacement as non-finite values in BVH can
lead to infinite node recursion during traversal.

Differential Revision: https://developer.blender.org/D12690

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

M	intern/cycles/kernel/kernel_bake.h

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

diff --git a/intern/cycles/kernel/kernel_bake.h b/intern/cycles/kernel/kernel_bake.h
index 7da890b908d..0f85963ff99 100644
--- a/intern/cycles/kernel/kernel_bake.h
+++ b/intern/cycles/kernel/kernel_bake.h
@@ -470,6 +470,16 @@ ccl_device void kernel_displace_evaluate(KernelGlobals *kg,
 
   object_inverse_dir_transform(kg, &sd, &D);
 
+#ifdef __KERNEL_DEBUG_NAN__
+  if (!isfinite3_safe(D)) {
+    kernel_assert(!"Cycles displacement with non-finite value detected");
+  }
+#endif
+
+  /* Ensure finite displacement, preventing BVH from becoming degenerate and avoiding possible
+   * traversal issues caused by non-finite math. */
+  D = ensure_finite3(D);
+
   /* write output */
   output[i] += make_float4(D.x, D.y, D.z, 0.0f);
 }
@@ -508,6 +518,15 @@ ccl_device void kernel_background_evaluate(KernelGlobals *kg,
   shader_eval_surface(kg, &sd, &state, NULL, path_flag | PATH_RAY_EMISSION);
   float3 color = shader_background_eval(&sd);
 
+#ifdef __KERNEL_DEBUG_NAN__
+  if (!isfinite3_safe(color)) {
+    kernel_assert(!"Cycles background with non-finite value detected");
+  }
+#endif
+
+  /* Ensure finite color, avoiding possible numerical instabilities in the path tracing kernels. */
+  color = ensure_finite3(color);
+
   /* write output */
   output[i] += make_float4(color.x, color.y, color.z, 0.0f);
 }