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

16 files changed, 116 insertions, 28 deletions

diff --git a/intern/cycles/kernel/closure/bsdf.h b/intern/cycles/kernel/closure/bsdf.h
index 50a047b3992..011155cdf5f 100644
--- a/intern/cycles/kernel/closure/bsdf.h
+++ b/intern/cycles/kernel/closure/bsdf.h
@@ -445,6 +445,11 @@ ccl_device_inline int bsdf_sample(KernelGlobals kg,
     }
   }
 
+#ifdef WITH_CYCLES_DEBUG
+  kernel_assert(*pdf >= 0.0f);
+  kernel_assert(eval->x >= 0.0f && eval->y >= 0.0f && eval->z >= 0.0f);
+#endif
+
   return label;
 }
 
@@ -635,7 +640,10 @@ ccl_device_inline
       }
     }
   }
-
+#ifdef WITH_CYCLES_DEBUG
+  kernel_assert(*pdf >= 0.0f);
+  kernel_assert(eval.x >= 0.0f && eval.y >= 0.0f && eval.z >= 0.0f);
+#endif
   return eval;
 }
 
diff --git a/intern/cycles/kernel/closure/bsdf_ashikhmin_shirley.h b/intern/cycles/kernel/closure/bsdf_ashikhmin_shirley.h
index a7694062935..47066542122 100644
--- a/intern/cycles/kernel/closure/bsdf_ashikhmin_shirley.h
+++ b/intern/cycles/kernel/closure/bsdf_ashikhmin_shirley.h
@@ -53,9 +53,10 @@ bsdf_ashikhmin_shirley_eval_reflect(ccl_private const ShaderClosure *sc,
 
   float out = 0.0f;
 
-  if (fmaxf(bsdf->alpha_x, bsdf->alpha_y) <= 1e-4f)
+  if (fmaxf(bsdf->alpha_x, bsdf->alpha_y) <= 1e-4f) {
+    *pdf = 0.0f;
     return make_float3(0.0f, 0.0f, 0.0f);
-
+  }
   if (NdotI > 0.0f && NdotO > 0.0f) {
     NdotI = fmaxf(NdotI, 1e-6f);
     NdotO = fmaxf(NdotO, 1e-6f);
@@ -112,6 +113,7 @@ ccl_device float3 bsdf_ashikhmin_shirley_eval_transmit(ccl_private const ShaderC
                                                        const float3 omega_in,
                                                        ccl_private float *pdf)
 {
+  *pdf = 0.0f;
   return make_float3(0.0f, 0.0f, 0.0f);
 }
 
diff --git a/intern/cycles/kernel/closure/bsdf_ashikhmin_velvet.h b/intern/cycles/kernel/closure/bsdf_ashikhmin_velvet.h
index d396e601338..3d7906eef7d 100644
--- a/intern/cycles/kernel/closure/bsdf_ashikhmin_velvet.h
+++ b/intern/cycles/kernel/closure/bsdf_ashikhmin_velvet.h
@@ -48,9 +48,10 @@ ccl_device float3 bsdf_ashikhmin_velvet_eval_reflect(ccl_private const ShaderClo
     float cosNH = dot(N, H);
     float cosHO = fabsf(dot(I, H));
 
-    if (!(fabsf(cosNH) < 1.0f - 1e-5f && cosHO > 1e-5f))
+    if (!(fabsf(cosNH) < 1.0f - 1e-5f && cosHO > 1e-5f)) {
+      *pdf = 0.0f;
       return make_float3(0.0f, 0.0f, 0.0f);
-
+    }
     float cosNHdivHO = cosNH / cosHO;
     cosNHdivHO = fmaxf(cosNHdivHO, 1e-5f);
 
@@ -62,7 +63,7 @@ ccl_device float3 bsdf_ashikhmin_velvet_eval_reflect(ccl_private const ShaderClo
     float cotangent2 = (cosNH * cosNH) / sinNH2;
 
     float D = expf(-cotangent2 * m_invsigma2) * m_invsigma2 * M_1_PI_F / sinNH4;
-    float G = min(1.0f, min(fac1, fac2));  // TODO: derive G from D analytically
+    float G = fminf(1.0f, fminf(fac1, fac2));  // TODO: derive G from D analytically
 
     float out = 0.25f * (D * G) / cosNO;
 
@@ -70,6 +71,7 @@ ccl_device float3 bsdf_ashikhmin_velvet_eval_reflect(ccl_private const ShaderClo
     return make_float3(out, out, out);
   }
 
+  *pdf = 0.0f;
   return make_float3(0.0f, 0.0f, 0.0f);
 }
 
@@ -78,6 +80,7 @@ ccl_device float3 bsdf_ashikhmin_velvet_eval_transmit(ccl_private const ShaderCl
                                                       const float3 omega_in,
                                                       ccl_private float *pdf)
 {
+  *pdf = 0.0f;
   return make_float3(0.0f, 0.0f, 0.0f);
 }
 
@@ -122,7 +125,7 @@ ccl_device int bsdf_ashikhmin_velvet_sample(ccl_private const ShaderClosure *sc,
       float cotangent2 = (cosNH * cosNH) / sinNH2;
 
       float D = expf(-cotangent2 * m_invsigma2) * m_invsigma2 * M_1_PI_F / sinNH4;
-      float G = min(1.0f, min(fac1, fac2));  // TODO: derive G from D analytically
+      float G = fminf(1.0f, fminf(fac1, fac2));  // TODO: derive G from D analytically
 
       float power = 0.25f * (D * G) / cosNO;
 
@@ -134,12 +137,15 @@ ccl_device int bsdf_ashikhmin_velvet_sample(ccl_private const ShaderClosure *sc,
       *domega_in_dy = (2 * dot(N, dIdy)) * N - dIdy;
 #endif
     }
-    else
+    else {
       *pdf = 0.0f;
+      *eval = make_float3(0.0f, 0.0f, 0.0f);
+    }
   }
-  else
+  else {
     *pdf = 0.0f;
-
+    *eval = make_float3(0.0f, 0.0f, 0.0f);
+  }
   return LABEL_REFLECT | LABEL_DIFFUSE;
 }
 
diff --git a/intern/cycles/kernel/closure/bsdf_diffuse.h b/intern/cycles/kernel/closure/bsdf_diffuse.h
index 18abdac8128..759ad03f8e8 100644
--- a/intern/cycles/kernel/closure/bsdf_diffuse.h
+++ b/intern/cycles/kernel/closure/bsdf_diffuse.h
@@ -44,6 +44,7 @@ ccl_device float3 bsdf_diffuse_eval_transmit(ccl_private const ShaderClosure *sc
                                              const float3 omega_in,
                                              ccl_private float *pdf)
 {
+  *pdf = 0.0f;
   return make_float3(0.0f, 0.0f, 0.0f);
 }
 
@@ -74,9 +75,10 @@ ccl_device int bsdf_diffuse_sample(ccl_private const ShaderClosure *sc,
     *domega_in_dy = (2 * dot(N, dIdy)) * N - dIdy;
 #endif
   }
-  else
+  else {
     *pdf = 0.0f;
-
+    *eval = make_float3(0.0f, 0.0f, 0.0f);
+  }
   return LABEL_REFLECT | LABEL_DIFFUSE;
 }
 
@@ -93,6 +95,7 @@ ccl_device float3 bsdf_translucent_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);
 }
 
@@ -138,6 +141,7 @@ ccl_device int bsdf_translucent_sample(ccl_private const ShaderClosure *sc,
   }
   else {
     *pdf = 0;
+    *eval = make_float3(0.0f, 0.0f, 0.0f);
   }
   return LABEL_TRANSMIT | LABEL_DIFFUSE;
 }
diff --git a/intern/cycles/kernel/closure/bsdf_diffuse_ramp.h b/intern/cycles/kernel/closure/bsdf_diffuse_ramp.h
index d1e31641431..aa4c091f587 100644
--- a/intern/cycles/kernel/closure/bsdf_diffuse_ramp.h
+++ b/intern/cycles/kernel/closure/bsdf_diffuse_ramp.h
@@ -93,9 +93,10 @@ ccl_device int bsdf_diffuse_ramp_sample(ccl_private const ShaderClosure *sc,
     *domega_in_dy = (2 * dot(N, dIdy)) * N - dIdy;
 #  endif
   }
-  else
+  else {
     *pdf = 0.0f;
-
+    *eval = make_float3(0.0f, 0.0f, 0.0f);
+  }
   return LABEL_REFLECT | LABEL_DIFFUSE;
 }
 
diff --git a/intern/cycles/kernel/closure/bsdf_hair.h b/intern/cycles/kernel/closure/bsdf_hair.h
index 0554d6e92fc..a136ed05800 100644
--- a/intern/cycles/kernel/closure/bsdf_hair.h
+++ b/intern/cycles/kernel/closure/bsdf_hair.h
@@ -89,6 +89,7 @@ ccl_device float3 bsdf_hair_transmission_eval_reflect(ccl_private const ShaderCl
                                                       const float3 omega_in,
                                                       ccl_private float *pdf)
 {
+  *pdf = 0.0f;
   return make_float3(0.0f, 0.0f, 0.0f);
 }
 
@@ -97,6 +98,7 @@ ccl_device float3 bsdf_hair_reflection_eval_transmit(ccl_private const ShaderClo
                                                      const float3 omega_in,
                                                      ccl_private float *pdf)
 {
+  *pdf = 0.0f;
   return make_float3(0.0f, 0.0f, 0.0f);
 }
 
diff --git a/intern/cycles/kernel/closure/bsdf_microfacet.h b/intern/cycles/kernel/closure/bsdf_microfacet.h
index d4c3c3509db..db50712f9f0 100644
--- a/intern/cycles/kernel/closure/bsdf_microfacet.h
+++ b/intern/cycles/kernel/closure/bsdf_microfacet.h
@@ -368,8 +368,10 @@ ccl_device float3 bsdf_microfacet_ggx_eval_reflect(ccl_private const ShaderClosu
   bool m_refractive = bsdf->type == CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID;
   float3 N = bsdf->N;
 
-  if (m_refractive || alpha_x * alpha_y <= 1e-7f)
+  if (m_refractive || alpha_x * alpha_y <= 1e-7f) {
+    *pdf = 0.0f;
     return make_float3(0.0f, 0.0f, 0.0f);
+  }
 
   float cosNO = dot(N, I);
   float cosNI = dot(N, omega_in);
@@ -482,15 +484,18 @@ ccl_device float3 bsdf_microfacet_ggx_eval_transmit(ccl_private const ShaderClos
   bool m_refractive = bsdf->type == CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID;
   float3 N = bsdf->N;
 
-  if (!m_refractive || alpha_x * alpha_y <= 1e-7f)
+  if (!m_refractive || alpha_x * alpha_y <= 1e-7f) {
+    *pdf = 0.0f;
     return make_float3(0.0f, 0.0f, 0.0f);
+  }
 
   float cosNO = dot(N, I);
   float cosNI = dot(N, omega_in);
 
-  if (cosNO <= 0 || cosNI >= 0)
+  if (cosNO <= 0 || cosNI >= 0) {
+    *pdf = 0.0f;
     return make_float3(0.0f, 0.0f, 0.0f); /* vectors on same side -- not possible */
-
+  }
   /* compute half-vector of the refraction (eq. 16) */
   float3 ht = -(m_eta * omega_in + I);
   float3 Ht = normalize(ht);
@@ -673,6 +678,10 @@ ccl_device int bsdf_microfacet_ggx_sample(KernelGlobals kg,
           *domega_in_dy = (2 * dot(m, dIdy)) * m - dIdy;
 #endif
         }
+        else {
+          *eval = make_float3(0.0f, 0.0f, 0.0f);
+          *pdf = 0.0f;
+        }
       }
     }
     else {
@@ -744,6 +753,10 @@ ccl_device int bsdf_microfacet_ggx_sample(KernelGlobals kg,
           *eval = make_float3(out, out, out);
         }
       }
+      else {
+        *eval = make_float3(0.0f, 0.0f, 0.0f);
+        *pdf = 0.0f;
+      }
     }
   }
   else {
@@ -833,8 +846,10 @@ ccl_device float3 bsdf_microfacet_beckmann_eval_reflect(ccl_private const Shader
   bool m_refractive = bsdf->type == CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID;
   float3 N = bsdf->N;
 
-  if (m_refractive || alpha_x * alpha_y <= 1e-7f)
+  if (m_refractive || alpha_x * alpha_y <= 1e-7f) {
+    *pdf = 0.0f;
     return make_float3(0.0f, 0.0f, 0.0f);
+  }
 
   float cosNO = dot(N, I);
   float cosNI = dot(N, omega_in);
@@ -913,15 +928,18 @@ ccl_device float3 bsdf_microfacet_beckmann_eval_transmit(ccl_private const Shade
   bool m_refractive = bsdf->type == CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID;
   float3 N = bsdf->N;
 
-  if (!m_refractive || alpha_x * alpha_y <= 1e-7f)
+  if (!m_refractive || alpha_x * alpha_y <= 1e-7f) {
+    *pdf = 0.0f;
     return make_float3(0.0f, 0.0f, 0.0f);
+  }
 
   float cosNO = dot(N, I);
   float cosNI = dot(N, omega_in);
 
-  if (cosNO <= 0 || cosNI >= 0)
+  if (cosNO <= 0 || cosNI >= 0) {
+    *pdf = 0.0f;
     return make_float3(0.0f, 0.0f, 0.0f);
-
+  }
   /* compute half-vector of the refraction (eq. 16) */
   float3 ht = -(m_eta * omega_in + I);
   float3 Ht = normalize(ht);
@@ -1064,6 +1082,10 @@ ccl_device int bsdf_microfacet_beckmann_sample(KernelGlobals kg,
           *domega_in_dy = (2 * dot(m, dIdy)) * m - dIdy;
 #endif
         }
+        else {
+          *eval = make_float3(0.0f, 0.0f, 0.0f);
+          *pdf = 0.0f;
+        }
       }
     }
     else {
@@ -1136,6 +1158,10 @@ ccl_device int bsdf_microfacet_beckmann_sample(KernelGlobals kg,
           *eval = make_float3(out, out, out);
         }
       }
+      else {
+        *eval = make_float3(0.0f, 0.0f, 0.0f);
+        *pdf = 0.0f;
+      }
     }
   }
   else {
diff --git a/intern/cycles/kernel/closure/bsdf_microfacet_multi.h b/intern/cycles/kernel/closure/bsdf_microfacet_multi.h
index 5aa9c8f0b16..c646c9ef01d 100644
--- a/intern/cycles/kernel/closure/bsdf_microfacet_multi.h
+++ b/intern/cycles/kernel/closure/bsdf_microfacet_multi.h
@@ -434,6 +434,7 @@ ccl_device float3 bsdf_microfacet_multi_ggx_eval_reflect(ccl_private const Shade
   ccl_private const MicrofacetBsdf *bsdf = (ccl_private const MicrofacetBsdf *)sc;
 
   if (bsdf->alpha_x * bsdf->alpha_y < 1e-7f) {
+    *pdf = 0.0f;
     return make_float3(0.0f, 0.0f, 0.0f);
   }
 
@@ -572,6 +573,7 @@ bsdf_microfacet_multi_ggx_glass_eval_transmit(ccl_private const ShaderClosure *s
   ccl_private const MicrofacetBsdf *bsdf = (ccl_private const MicrofacetBsdf *)sc;
 
   if (bsdf->alpha_x * bsdf->alpha_y < 1e-7f) {
+    *pdf = 0.0f;
     return make_float3(0.0f, 0.0f, 0.0f);
   }
 
@@ -604,6 +606,7 @@ ccl_device float3 bsdf_microfacet_multi_ggx_glass_eval_reflect(ccl_private const
   ccl_private const MicrofacetBsdf *bsdf = (ccl_private const MicrofacetBsdf *)sc;
 
   if (bsdf->alpha_x * bsdf->alpha_y < 1e-7f) {
+    *pdf = 0.0f;
     return make_float3(0.0f, 0.0f, 0.0f);
   }
 
diff --git a/intern/cycles/kernel/closure/bsdf_oren_nayar.h b/intern/cycles/kernel/closure/bsdf_oren_nayar.h
index 47ad7b85942..56c7ec869c7 100644
--- a/intern/cycles/kernel/closure/bsdf_oren_nayar.h
+++ b/intern/cycles/kernel/closure/bsdf_oren_nayar.h
@@ -68,6 +68,7 @@ ccl_device float3 bsdf_oren_nayar_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);
 }
 
diff --git a/intern/cycles/kernel/closure/bsdf_phong_ramp.h b/intern/cycles/kernel/closure/bsdf_phong_ramp.h
index 819c51e2935..74a1f7ae090 100644
--- a/intern/cycles/kernel/closure/bsdf_phong_ramp.h
+++ b/intern/cycles/kernel/closure/bsdf_phong_ramp.h
@@ -64,7 +64,7 @@ ccl_device float3 bsdf_phong_ramp_eval_reflect(ccl_private const ShaderClosure *
       return bsdf_phong_ramp_get_color(bsdf->colors, cosp) * out;
     }
   }
-
+  *pdf = 0.0f;
   return make_float3(0.0f, 0.0f, 0.0f);
 }
 
@@ -73,6 +73,7 @@ ccl_device float3 bsdf_phong_ramp_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);
 }
 
@@ -122,6 +123,10 @@ ccl_device int bsdf_phong_ramp_sample(ccl_private const ShaderClosure *sc,
       }
     }
   }
+  else {
+    *eval = make_float3(0.0f, 0.0f, 0.0f);
+    *pdf = 0.0f;
+  }
   return LABEL_REFLECT | LABEL_GLOSSY;
 }
 
diff --git a/intern/cycles/kernel/closure/bsdf_principled_diffuse.h b/intern/cycles/kernel/closure/bsdf_principled_diffuse.h
index 208540bd388..5a7020e82d2 100644
--- a/intern/cycles/kernel/closure/bsdf_principled_diffuse.h
+++ b/intern/cycles/kernel/closure/bsdf_principled_diffuse.h
@@ -135,6 +135,7 @@ ccl_device float3 bsdf_principled_diffuse_eval_transmit(ccl_private const Shader
                                                         const float3 omega_in,
                                                         ccl_private float *pdf)
 {
+  *pdf = 0.0f;
   return make_float3(0.0f, 0.0f, 0.0f);
 }
 
@@ -168,6 +169,7 @@ ccl_device int bsdf_principled_diffuse_sample(ccl_private const ShaderClosure *s
   }
   else {
     *pdf = 0.0f;
+    *eval = make_float3(0.0f, 0.0f, 0.0f);
   }
   return LABEL_REFLECT | LABEL_DIFFUSE;
 }
diff --git a/intern/cycles/kernel/closure/bsdf_principled_sheen.h b/intern/cycles/kernel/closure/bsdf_principled_sheen.h
index ea2ea03adb9..3a96a93db73 100644
--- a/intern/cycles/kernel/closure/bsdf_principled_sheen.h
+++ b/intern/cycles/kernel/closure/bsdf_principled_sheen.h
@@ -86,6 +86,7 @@ ccl_device float3 bsdf_principled_sheen_eval_transmit(ccl_private const ShaderCl
                                                       const float3 omega_in,
                                                       ccl_private float *pdf)
 {
+  *pdf = 0.0f;
   return make_float3(0.0f, 0.0f, 0.0f);
 }
 
@@ -120,6 +121,7 @@ ccl_device int bsdf_principled_sheen_sample(ccl_private const ShaderClosure *sc,
 #endif
   }
   else {
+    *eval = make_float3(0.0f, 0.0f, 0.0f);
     *pdf = 0.0f;
   }
   return LABEL_REFLECT | LABEL_DIFFUSE;
diff --git a/intern/cycles/kernel/closure/bsdf_reflection.h b/intern/cycles/kernel/closure/bsdf_reflection.h
index 6887c4b09a0..c8db2b7cf13 100644
--- a/intern/cycles/kernel/closure/bsdf_reflection.h
+++ b/intern/cycles/kernel/closure/bsdf_reflection.h
@@ -23,6 +23,7 @@ ccl_device float3 bsdf_reflection_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);
 }
 
@@ -31,6 +32,7 @@ ccl_device float3 bsdf_reflection_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);
 }
 
@@ -64,6 +66,10 @@ ccl_device int bsdf_reflection_sample(ccl_private const ShaderClosure *sc,
       *eval = make_float3(1e6f, 1e6f, 1e6f);
     }
   }
+  else {
+    *pdf = 0.0f;
+    *eval = make_float3(0.0f, 0.0f, 0.0f);
+  }
   return LABEL_REFLECT | LABEL_SINGULAR;
 }
 
diff --git a/intern/cycles/kernel/closure/bsdf_refraction.h b/intern/cycles/kernel/closure/bsdf_refraction.h
index 88497525960..862e774da87 100644
--- a/intern/cycles/kernel/closure/bsdf_refraction.h
+++ b/intern/cycles/kernel/closure/bsdf_refraction.h
@@ -23,6 +23,7 @@ ccl_device float3 bsdf_refraction_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);
 }
 
@@ -31,6 +32,7 @@ ccl_device float3 bsdf_refraction_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);
 }
 
@@ -82,6 +84,10 @@ ccl_device int bsdf_refraction_sample(ccl_private const ShaderClosure *sc,
     *domega_in_dy = dTdy;
 #endif
   }
+  else {
+    *pdf = 0.0f;
+    *eval = make_float3(0.0f, 0.0f, 0.0f);
+  }
   return LABEL_TRANSMIT | LABEL_SINGULAR;
 }
 
diff --git a/intern/cycles/kernel/closure/bsdf_toon.h b/intern/cycles/kernel/closure/bsdf_toon.h
index 53ccb683721..0400fc61860 100644
--- a/intern/cycles/kernel/closure/bsdf_toon.h
+++ b/intern/cycles/kernel/closure/bsdf_toon.h
@@ -67,7 +67,7 @@ ccl_device float3 bsdf_diffuse_toon_eval_reflect(ccl_private const ShaderClosure
     *pdf = 0.5f * M_1_PI_F / (1.0f - cosf(sample_angle));
     return *pdf * eval;
   }
-
+  *pdf = 0.0f;
   return make_float3(0.0f, 0.0f, 0.0f);
 }
 
@@ -76,6 +76,7 @@ ccl_device float3 bsdf_diffuse_toon_eval_transmit(ccl_private const ShaderClosur
                                                   const float3 omega_in,
                                                   ccl_private float *pdf)
 {
+  *pdf = 0.0f;
   return make_float3(0.0f, 0.0f, 0.0f);
 }
 
@@ -110,8 +111,14 @@ ccl_device int bsdf_diffuse_toon_sample(ccl_private const ShaderClosure *sc,
       *domega_in_dy = (2.0f * dot(bsdf->N, dIdy)) * bsdf->N - dIdy;
 #endif
     }
-    else
+    else {
+      *eval = make_float3(0.f, 0.f, 0.f);
       *pdf = 0.0f;
+    }
+  }
+  else {
+    *eval = make_float3(0.f, 0.f, 0.f);
+    *pdf = 0.0f;
   }
 
   return LABEL_REFLECT | LABEL_DIFFUSE;
@@ -152,7 +159,7 @@ ccl_device float3 bsdf_glossy_toon_eval_reflect(ccl_private const ShaderClosure
     *pdf = 0.5f * M_1_PI_F / (1.0f - cosf(sample_angle));
     return *pdf * eval;
   }
-
+  *pdf = 0.0f;
   return make_float3(0.0f, 0.0f, 0.0f);
 }
 
@@ -161,6 +168,7 @@ ccl_device float3 bsdf_glossy_toon_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);
 }
 
@@ -203,11 +211,15 @@ ccl_device int bsdf_glossy_toon_sample(ccl_private const ShaderClosure *sc,
         *domega_in_dy = (2 * dot(bsdf->N, dIdy)) * bsdf->N - dIdy;
 #endif
       }
-      else
+      else {
         *pdf = 0.0f;
+        *eval = make_float3(0.0f, 0.0f, 0.0f);
+      }
     }
-    else
+    else {
       *pdf = 0.0f;
+      *eval = make_float3(0.0f, 0.0f, 0.0f);
+    }
   }
 
   return LABEL_GLOSSY | LABEL_REFLECT;
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);
 }