Cycles: BSDF changes in preparation of path guiding

* Return roughness and IOR for BSDF sampling
* Add functions to query IOR and label for given BSDF
* Default IOR to 1.0 instead of 0.0 for BSDFs that don't use it
* Ensure pdf >= 0.0 in case of numerical precision issues

Ref T92571, D15286

1 files changed, 309 insertions, 14 deletions

diff --git a/intern/cycles/kernel/closure/bsdf.h b/intern/cycles/kernel/closure/bsdf.h
index f0b28ff77c4..d202018be9a 100644
--- a/intern/cycles/kernel/closure/bsdf.h
+++ b/intern/cycles/kernel/closure/bsdf.h
@@ -105,7 +105,9 @@ ccl_device_inline int bsdf_sample(KernelGlobals kg,
                                   float randv,
                                   ccl_private Spectrum *eval,
                                   ccl_private float3 *omega_in,
-                                  ccl_private float *pdf)
+                                  ccl_private float *pdf,
+                                  ccl_private float2 *sampled_roughness,
+                                  ccl_private float *eta)
 {
   /* For curves use the smooth normal, particularly for ribbons the geometric
    * normal gives too much darkening otherwise. */
@@ -115,78 +117,131 @@ ccl_device_inline int bsdf_sample(KernelGlobals kg,
   switch (sc->type) {
     case CLOSURE_BSDF_DIFFUSE_ID:
       label = bsdf_diffuse_sample(sc, Ng, sd->I, randu, randv, eval, omega_in, pdf);
+      *sampled_roughness = one_float2();
+      *eta = 1.0f;
       break;
 #if defined(__SVM__) || defined(__OSL__)
     case CLOSURE_BSDF_OREN_NAYAR_ID:
       label = bsdf_oren_nayar_sample(sc, Ng, sd->I, randu, randv, eval, omega_in, pdf);
+      *sampled_roughness = one_float2();
+      *eta = 1.0f;
       break;
 #  ifdef __OSL__
     case CLOSURE_BSDF_PHONG_RAMP_ID:
-      label = bsdf_phong_ramp_sample(sc, Ng, sd->I, randu, randv, eval, omega_in, pdf);
+      label = bsdf_phong_ramp_sample(
+          sc, Ng, sd->I, randu, randv, eval, omega_in, pdf, sampled_roughness);
+      *eta = 1.0f;
       break;
     case CLOSURE_BSDF_DIFFUSE_RAMP_ID:
       label = bsdf_diffuse_ramp_sample(sc, Ng, sd->I, randu, randv, eval, omega_in, pdf);
+      *sampled_roughness = one_float2();
+      *eta = 1.0f;
       break;
 #  endif
     case CLOSURE_BSDF_TRANSLUCENT_ID:
       label = bsdf_translucent_sample(sc, Ng, sd->I, randu, randv, eval, omega_in, pdf);
+      *sampled_roughness = one_float2();
+      *eta = 1.0f;
       break;
     case CLOSURE_BSDF_REFLECTION_ID:
-      label = bsdf_reflection_sample(sc, Ng, sd->I, randu, randv, eval, omega_in, pdf);
+      label = bsdf_reflection_sample(sc, Ng, sd->I, randu, randv, eval, omega_in, pdf, eta);
+      *sampled_roughness = zero_float2();
       break;
     case CLOSURE_BSDF_REFRACTION_ID:
-      label = bsdf_refraction_sample(sc, Ng, sd->I, randu, randv, eval, omega_in, pdf);
+      label = bsdf_refraction_sample(sc, Ng, sd->I, randu, randv, eval, omega_in, pdf, eta);
+      *sampled_roughness = zero_float2();
       break;
     case CLOSURE_BSDF_TRANSPARENT_ID:
       label = bsdf_transparent_sample(sc, Ng, sd->I, randu, randv, eval, omega_in, pdf);
+      *sampled_roughness = zero_float2();
+      *eta = 1.0f;
       break;
     case CLOSURE_BSDF_MICROFACET_GGX_ID:
     case CLOSURE_BSDF_MICROFACET_GGX_FRESNEL_ID:
     case CLOSURE_BSDF_MICROFACET_GGX_CLEARCOAT_ID:
     case CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID:
-      label = bsdf_microfacet_ggx_sample(kg, sc, Ng, sd->I, randu, randv, eval, omega_in, pdf);
+      label = bsdf_microfacet_ggx_sample(
+          kg, sc, Ng, sd->I, randu, randv, eval, omega_in, pdf, sampled_roughness, eta);
       break;
     case CLOSURE_BSDF_MICROFACET_MULTI_GGX_ID:
     case CLOSURE_BSDF_MICROFACET_MULTI_GGX_FRESNEL_ID:
-      label = bsdf_microfacet_multi_ggx_sample(
-          kg, sc, Ng, sd->I, randu, randv, eval, omega_in, pdf, &sd->lcg_state);
+      label = bsdf_microfacet_multi_ggx_sample(kg,
+                                               sc,
+                                               Ng,
+                                               sd->I,
+                                               randu,
+                                               randv,
+                                               eval,
+                                               omega_in,
+                                               pdf,
+                                               &sd->lcg_state,
+                                               sampled_roughness,
+                                               eta);
       break;
     case CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_ID:
     case CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_FRESNEL_ID:
-      label = bsdf_microfacet_multi_ggx_glass_sample(
-          kg, sc, Ng, sd->I, randu, randv, eval, omega_in, pdf, &sd->lcg_state);
+      label = bsdf_microfacet_multi_ggx_glass_sample(kg,
+                                                     sc,
+                                                     Ng,
+                                                     sd->I,
+                                                     randu,
+                                                     randv,
+                                                     eval,
+                                                     omega_in,
+                                                     pdf,
+                                                     &sd->lcg_state,
+                                                     sampled_roughness,
+                                                     eta);
       break;
     case CLOSURE_BSDF_MICROFACET_BECKMANN_ID:
     case CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID:
       label = bsdf_microfacet_beckmann_sample(
-          kg, sc, Ng, sd->I, randu, randv, eval, omega_in, pdf);
+          kg, sc, Ng, sd->I, randu, randv, eval, omega_in, pdf, sampled_roughness, eta);
       break;
     case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID:
-      label = bsdf_ashikhmin_shirley_sample(sc, Ng, sd->I, randu, randv, eval, omega_in, pdf);
+      label = bsdf_ashikhmin_shirley_sample(
+          sc, Ng, sd->I, randu, randv, eval, omega_in, pdf, sampled_roughness);
+      *eta = 1.0f;
       break;
     case CLOSURE_BSDF_ASHIKHMIN_VELVET_ID:
       label = bsdf_ashikhmin_velvet_sample(sc, Ng, sd->I, randu, randv, eval, omega_in, pdf);
+      *sampled_roughness = one_float2();
+      *eta = 1.0f;
       break;
     case CLOSURE_BSDF_DIFFUSE_TOON_ID:
       label = bsdf_diffuse_toon_sample(sc, Ng, sd->I, randu, randv, eval, omega_in, pdf);
+      *sampled_roughness = one_float2();
+      *eta = 1.0f;
       break;
     case CLOSURE_BSDF_GLOSSY_TOON_ID:
       label = bsdf_glossy_toon_sample(sc, Ng, sd->I, randu, randv, eval, omega_in, pdf);
+      // double check if this is valid
+      *sampled_roughness = one_float2();
+      *eta = 1.0f;
       break;
     case CLOSURE_BSDF_HAIR_REFLECTION_ID:
-      label = bsdf_hair_reflection_sample(sc, Ng, sd->I, randu, randv, eval, omega_in, pdf);
+      label = bsdf_hair_reflection_sample(
+          sc, Ng, sd->I, randu, randv, eval, omega_in, pdf, sampled_roughness);
+      *eta = 1.0f;
       break;
     case CLOSURE_BSDF_HAIR_TRANSMISSION_ID:
-      label = bsdf_hair_transmission_sample(sc, Ng, sd->I, randu, randv, eval, omega_in, pdf);
+      label = bsdf_hair_transmission_sample(
+          sc, Ng, sd->I, randu, randv, eval, omega_in, pdf, sampled_roughness);
+      *eta = 1.0f;
       break;
     case CLOSURE_BSDF_HAIR_PRINCIPLED_ID:
-      label = bsdf_principled_hair_sample(kg, sc, sd, randu, randv, eval, omega_in, pdf);
+      label = bsdf_principled_hair_sample(
+          kg, sc, sd, randu, randv, eval, omega_in, pdf, sampled_roughness, eta);
       break;
     case CLOSURE_BSDF_PRINCIPLED_DIFFUSE_ID:
       label = bsdf_principled_diffuse_sample(sc, Ng, sd->I, randu, randv, eval, omega_in, pdf);
+      *sampled_roughness = one_float2();
+      *eta = 1.0f;
       break;
     case CLOSURE_BSDF_PRINCIPLED_SHEEN_ID:
       label = bsdf_principled_sheen_sample(sc, Ng, sd->I, randu, randv, eval, omega_in, pdf);
+      *sampled_roughness = one_float2();
+      *eta = 1.0f;
       break;
 #endif
     default:
@@ -226,6 +281,246 @@ ccl_device_inline int bsdf_sample(KernelGlobals kg,
   return label;
 }
 
+ccl_device_inline void bsdf_roughness_eta(const KernelGlobals kg,
+                                          ccl_private const ShaderClosure *sc,
+                                          ccl_private float2 *roughness,
+                                          ccl_private float *eta)
+{
+  bool refractive = false;
+  float alpha = 1.0f;
+  switch (sc->type) {
+    case CLOSURE_BSDF_DIFFUSE_ID:
+      *roughness = one_float2();
+      *eta = 1.0f;
+      break;
+#ifdef __SVM__
+    case CLOSURE_BSDF_OREN_NAYAR_ID:
+      *roughness = one_float2();
+      *eta = 1.0f;
+      break;
+#  ifdef __OSL__
+    case CLOSURE_BSDF_PHONG_RAMP_ID:
+      alpha = phong_ramp_exponent_to_roughness(((ccl_private const PhongRampBsdf *)sc)->exponent);
+      *roughness = make_float2(alpha, alpha);
+      *eta = 1.0f;
+      break;
+    case CLOSURE_BSDF_DIFFUSE_RAMP_ID:
+      *roughness = one_float2();
+      *eta = 1.0f;
+      break;
+#  endif
+    case CLOSURE_BSDF_TRANSLUCENT_ID:
+      *roughness = one_float2();
+      *eta = 1.0f;
+      break;
+    case CLOSURE_BSDF_REFLECTION_ID: {
+      ccl_private const MicrofacetBsdf *bsdf = (ccl_private const MicrofacetBsdf *)sc;
+      *roughness = zero_float2();
+      *eta = bsdf->ior;
+      break;
+    }
+    case CLOSURE_BSDF_REFRACTION_ID: {
+      ccl_private const MicrofacetBsdf *bsdf = (ccl_private const MicrofacetBsdf *)sc;
+      *roughness = zero_float2();
+      // do we need to inverse eta??
+      *eta = bsdf->ior;
+      break;
+    }
+    case CLOSURE_BSDF_TRANSPARENT_ID:
+      *roughness = zero_float2();
+      *eta = 1.0f;
+      break;
+    case CLOSURE_BSDF_MICROFACET_GGX_ID:
+    case CLOSURE_BSDF_MICROFACET_GGX_FRESNEL_ID:
+    case CLOSURE_BSDF_MICROFACET_GGX_CLEARCOAT_ID:
+    case CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID: {
+      ccl_private const MicrofacetBsdf *bsdf = (ccl_private const MicrofacetBsdf *)sc;
+      *roughness = make_float2(bsdf->alpha_x, bsdf->alpha_y);
+      refractive = bsdf->type == CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID;
+      *eta = refractive ? 1.0f / bsdf->ior : bsdf->ior;
+      break;
+    }
+    case CLOSURE_BSDF_MICROFACET_MULTI_GGX_ID:
+    case CLOSURE_BSDF_MICROFACET_MULTI_GGX_FRESNEL_ID: {
+      ccl_private const MicrofacetBsdf *bsdf = (ccl_private const MicrofacetBsdf *)sc;
+      *roughness = make_float2(bsdf->alpha_x, bsdf->alpha_y);
+      *eta = bsdf->ior;
+      break;
+    }
+    case CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_ID:
+    case CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_FRESNEL_ID: {
+      ccl_private const MicrofacetBsdf *bsdf = (ccl_private const MicrofacetBsdf *)sc;
+      *roughness = make_float2(bsdf->alpha_x, bsdf->alpha_y);
+      *eta = bsdf->ior;
+      break;
+    }
+    case CLOSURE_BSDF_MICROFACET_BECKMANN_ID:
+    case CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID: {
+      ccl_private const MicrofacetBsdf *bsdf = (ccl_private const MicrofacetBsdf *)sc;
+      *roughness = make_float2(bsdf->alpha_x, bsdf->alpha_y);
+      refractive = bsdf->type == CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID;
+      *eta = refractive ? 1.0f / bsdf->ior : bsdf->ior;
+    } break;
+    case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID: {
+      ccl_private const MicrofacetBsdf *bsdf = (ccl_private const MicrofacetBsdf *)sc;
+      *roughness = make_float2(bsdf->alpha_x, bsdf->alpha_y);
+      *eta = 1.0f;
+      break;
+    }
+    case CLOSURE_BSDF_ASHIKHMIN_VELVET_ID:
+      *roughness = one_float2();
+      *eta = 1.0f;
+      break;
+    case CLOSURE_BSDF_DIFFUSE_TOON_ID:
+      *roughness = one_float2();
+      *eta = 1.0f;
+      break;
+    case CLOSURE_BSDF_GLOSSY_TOON_ID:
+      // double check if this is valid
+      *roughness = one_float2();
+      *eta = 1.0f;
+      break;
+    case CLOSURE_BSDF_HAIR_REFLECTION_ID:
+      *roughness = make_float2(((ccl_private HairBsdf *)sc)->roughness1,
+                               ((ccl_private HairBsdf *)sc)->roughness2);
+      *eta = 1.0f;
+      break;
+    case CLOSURE_BSDF_HAIR_TRANSMISSION_ID:
+      *roughness = make_float2(((ccl_private HairBsdf *)sc)->roughness1,
+                               ((ccl_private HairBsdf *)sc)->roughness2);
+      *eta = 1.0f;
+      break;
+    case CLOSURE_BSDF_HAIR_PRINCIPLED_ID:
+      alpha = ((ccl_private PrincipledHairBSDF *)sc)->m0_roughness;
+      *roughness = make_float2(alpha, alpha);
+      *eta = ((ccl_private PrincipledHairBSDF *)sc)->eta;
+      break;
+    case CLOSURE_BSDF_PRINCIPLED_DIFFUSE_ID:
+      *roughness = one_float2();
+      *eta = 1.0f;
+      break;
+    case CLOSURE_BSDF_PRINCIPLED_SHEEN_ID:
+      *roughness = one_float2();
+      *eta = 1.0f;
+      break;
+#endif
+    default:
+      *roughness = one_float2();
+      *eta = 1.0f;
+      break;
+  }
+}
+
+ccl_device_inline int bsdf_label(const KernelGlobals kg,
+                                 ccl_private const ShaderClosure *sc,
+                                 const float3 omega_in)
+{
+  /* For curves use the smooth normal, particularly for ribbons the geometric
+   * normal gives too much darkening otherwise. */
+  int label;
+  switch (sc->type) {
+    case CLOSURE_BSDF_DIFFUSE_ID:
+    case CLOSURE_BSSRDF_BURLEY_ID:
+    case CLOSURE_BSSRDF_RANDOM_WALK_ID:
+    case CLOSURE_BSSRDF_RANDOM_WALK_FIXED_RADIUS_ID:
+      label = LABEL_REFLECT | LABEL_DIFFUSE;
+      break;
+#ifdef __SVM__
+    case CLOSURE_BSDF_OREN_NAYAR_ID:
+      label = LABEL_REFLECT | LABEL_DIFFUSE;
+      break;
+#  ifdef __OSL__
+    case CLOSURE_BSDF_PHONG_RAMP_ID:
+      label = LABEL_REFLECT | LABEL_GLOSSY;
+      break;
+    case CLOSURE_BSDF_DIFFUSE_RAMP_ID:
+      label = LABEL_REFLECT | LABEL_DIFFUSE;
+      break;
+#  endif
+    case CLOSURE_BSDF_TRANSLUCENT_ID:
+      label = LABEL_TRANSMIT | LABEL_DIFFUSE;
+      break;
+    case CLOSURE_BSDF_REFLECTION_ID:
+      label = LABEL_REFLECT | LABEL_SINGULAR;
+      break;
+    case CLOSURE_BSDF_REFRACTION_ID:
+      label = LABEL_TRANSMIT | LABEL_SINGULAR;
+      break;
+    case CLOSURE_BSDF_TRANSPARENT_ID:
+      label = LABEL_TRANSMIT | LABEL_TRANSPARENT;
+      break;
+    case CLOSURE_BSDF_MICROFACET_GGX_ID:
+    case CLOSURE_BSDF_MICROFACET_GGX_FRESNEL_ID:
+    case CLOSURE_BSDF_MICROFACET_GGX_CLEARCOAT_ID:
+    case CLOSURE_BSDF_MICROFACET_MULTI_GGX_ID:
+    case CLOSURE_BSDF_MICROFACET_MULTI_GGX_FRESNEL_ID:
+    case CLOSURE_BSDF_MICROFACET_BECKMANN_ID: {
+      ccl_private const MicrofacetBsdf *bsdf = (ccl_private const MicrofacetBsdf *)sc;
+      label = (bsdf->alpha_x * bsdf->alpha_y <= 1e-7f) ? LABEL_REFLECT | LABEL_SINGULAR :
+                                                         LABEL_REFLECT | LABEL_GLOSSY;
+      break;
+    }
+    case CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID:
+    case CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID: {
+      ccl_private const MicrofacetBsdf *bsdf = (ccl_private const MicrofacetBsdf *)sc;
+      label = (bsdf->alpha_x * bsdf->alpha_y <= 1e-7f) ? LABEL_TRANSMIT | LABEL_SINGULAR :
+                                                         LABEL_TRANSMIT | LABEL_GLOSSY;
+      break;
+    }
+    case CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_ID:
+    case CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_FRESNEL_ID:
+      label = (bsdf_is_transmission(sc, omega_in)) ? LABEL_TRANSMIT | LABEL_GLOSSY :
+                                                     LABEL_REFLECT | LABEL_GLOSSY;
+      break;
+    case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID:
+      label = LABEL_REFLECT | LABEL_GLOSSY;
+      break;
+    case CLOSURE_BSDF_ASHIKHMIN_VELVET_ID:
+      label = LABEL_REFLECT | LABEL_DIFFUSE;
+      break;
+    case CLOSURE_BSDF_DIFFUSE_TOON_ID:
+      label = LABEL_REFLECT | LABEL_DIFFUSE;
+      break;
+    case CLOSURE_BSDF_GLOSSY_TOON_ID:
+      label = LABEL_REFLECT | LABEL_GLOSSY;
+      break;
+    case CLOSURE_BSDF_HAIR_REFLECTION_ID:
+      label = LABEL_REFLECT | LABEL_GLOSSY;
+      break;
+    case CLOSURE_BSDF_HAIR_TRANSMISSION_ID:
+      label = LABEL_TRANSMIT | LABEL_GLOSSY;
+      break;
+    case CLOSURE_BSDF_HAIR_PRINCIPLED_ID:
+      if (is_transmission)
+        label = LABEL_TRANSMIT | LABEL_GLOSSY;
+      else
+        label = LABEL_REFLECT | LABEL_GLOSSY;
+      break;
+    case CLOSURE_BSDF_PRINCIPLED_DIFFUSE_ID:
+      label = LABEL_REFLECT | LABEL_DIFFUSE;
+      break;
+    case CLOSURE_BSDF_PRINCIPLED_SHEEN_ID:
+      label = LABEL_REFLECT | LABEL_DIFFUSE;
+      break;
+#endif
+    default:
+      label = LABEL_NONE;
+      break;
+  }
+
+  /* Test if BSDF sample should be treated as transparent for background. */
+  if (label & LABEL_TRANSMIT) {
+    float threshold_squared = kernel_data.background.transparent_roughness_squared_threshold;
+
+    if (threshold_squared >= 0.0f) {
+      if (bsdf_get_specular_roughness_squared(sc) <= threshold_squared) {
+        label |= LABEL_TRANSMIT_TRANSPARENT;
+      }
+    }
+  }
+  return label;
+}
+
 #ifndef __KERNEL_CUDA__
 ccl_device
 #else