Ensure BSDF evals and pdfs are zero on invalid samples

Currently, the `eval` and `pdf` are not explicitly set to zero when a BSDF sample is invalid (e.g., below the upper hemisphere), when calling
`bsdf_sample` or `bsdf_eval`. It is assumed that `eval` and `pdf` are set to zero before these functions are called, which can cause problems if not.

This patch fixes this potential problem by explicitly setting `eval` and `pdf` to zero when the sampled direction is invalid.

I also added a sanity check if `eval` and `pdf` are valid (i.e., >= 0.f).
The check is activated when build in debug mode and with the `WITH_CYCLES_DEBUG` set to `ON`.

Reviewed By: brecht, sergey

Differential Revision: https://developer.blender.org/D14776

1 files changed, 2 insertions, 0 deletions

diff --git a/intern/cycles/kernel/closure/bsdf_transparent.h b/intern/cycles/kernel/closure/bsdf_transparent.h
index 2a0bd453009..636d9d664f2 100644
--- a/intern/cycles/kernel/closure/bsdf_transparent.h
+++ b/intern/cycles/kernel/closure/bsdf_transparent.h
@@ -64,6 +64,7 @@ ccl_device float3 bsdf_transparent_eval_reflect(ccl_private const ShaderClosure
                                                 const float3 omega_in,
                                                 ccl_private float *pdf)
 {
+  *pdf = 0.0f;
   return make_float3(0.0f, 0.0f, 0.0f);
 }
 
@@ -72,6 +73,7 @@ ccl_device float3 bsdf_transparent_eval_transmit(ccl_private const ShaderClosure
                                                  const float3 omega_in,
                                                  ccl_private float *pdf)
 {
+  *pdf = 0.0f;
   return make_float3(0.0f, 0.0f, 0.0f);
 }