Cycles: Refactor closure roughness detection to fix a potential bug with Denoising of specular shaders

intern/cycles/kernel/closure/bsdf.h

@@ -36,6 +36,22 @@
 
 CCL_NAMESPACE_BEGIN
 
+/* Returns the square of the roughness of the closure if it has roughness,
+ * 0 for singular closures and 1 otherwise. */
+ccl_device_inline float bsdf_get_roughness_sqr(const ShaderClosure *sc)
+{
+	if(CLOSURE_IS_BSDF_SINGULAR(sc->type)) {
+		return 0.0f;
+	}
+
+	if(CLOSURE_IS_BSDF_MICROFACET(sc->type)) {
+		MicrofacetBsdf *bsdf = (MicrofacetBsdf*) sc;
+		return bsdf->alpha_x*bsdf->alpha_y;
+	}
+
+	return 1.0f;
+}
+
 ccl_device_forceinline int bsdf_sample(KernelGlobals *kg,
                                        ShaderData *sd,
                                        const ShaderClosure *sc,
@@ -438,23 +454,5 @@ ccl_device bool bsdf_merge(ShaderClosure *a, ShaderClosure *b)
 #endif
 }
 
-/* Classifies a closure as diffuse-like or specular-like.
- * This is needed for the denoising feature pass generation,
- * which are written on the first bounce where more than 25%
- * of the sampling weight belongs to diffuse-line closures. */
-ccl_device_inline bool bsdf_is_specular_like(ShaderClosure *sc)
-{
-	if(CLOSURE_IS_BSDF_TRANSPARENT(sc->type)) {
-		return true;
-	}
-
-	if(CLOSURE_IS_BSDF_MICROFACET(sc->type)) {
-		MicrofacetBsdf *bsdf = (MicrofacetBsdf*) sc;
-		return (bsdf->alpha_x*bsdf->alpha_y <= 0.075f*0.075f);
-	}
-
-	return false;
-}
-
 CCL_NAMESPACE_END
 

intern/cycles/kernel/kernel_passes.h

@@ -140,7 +140,7 @@ ccl_device_inline void kernel_update_denoising_features(KernelGlobals *kg,
 		/* All closures contribute to the normal feature, but only diffuse-like ones to the albedo. */
 		normal += sc->N * sc->sample_weight;
 		sum_weight += sc->sample_weight;
-		if(!bsdf_is_specular_like(sc)) {
+		if(bsdf_get_roughness_sqr(sc) > sqr(0.075f)) {
 			albedo += sc->weight;
 			sum_nonspecular_weight += sc->sample_weight;
 		}

intern/cycles/kernel/svm/svm_types.h

@@ -465,13 +465,16 @@ typedef enum ClosureType {
 #define CLOSURE_IS_BSDF_GLOSSY(type) (type >= CLOSURE_BSDF_REFLECTION_ID && type <= CLOSURE_BSDF_HAIR_REFLECTION_ID)
 #define CLOSURE_IS_BSDF_TRANSMISSION(type) (type >= CLOSURE_BSDF_TRANSLUCENT_ID && type <= CLOSURE_BSDF_HAIR_TRANSMISSION_ID)
 #define CLOSURE_IS_BSDF_BSSRDF(type) (type == CLOSURE_BSDF_BSSRDF_ID || type == CLOSURE_BSDF_BSSRDF_PRINCIPLED_ID)
+#define CLOSURE_IS_BSDF_SINGULAR(type) (type == CLOSURE_BSDF_REFLECTION_ID || \
+                                        type == CLOSURE_BSDF_REFRACTION_ID || \
+                                        type == CLOSURE_BSDF_TRANSPARENT_ID)
 #define CLOSURE_IS_BSDF_TRANSPARENT(type) (type == CLOSURE_BSDF_TRANSPARENT_ID)
-#define CLOSURE_IS_BSDF_ANISOTROPIC(type) (type >= CLOSURE_BSDF_MICROFACET_GGX_ANISO_ID && type <= CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ANISO_ID)
 #define CLOSURE_IS_BSDF_MULTISCATTER(type) (type == CLOSURE_BSDF_MICROFACET_MULTI_GGX_ID ||\
                                             type == CLOSURE_BSDF_MICROFACET_MULTI_GGX_ANISO_ID || \
                                             type == CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_ID)
-#define CLOSURE_IS_BSDF_MICROFACET(type) ((type >= CLOSURE_BSDF_REFLECTION_ID && type <= CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ANISO_ID) ||\
+#define CLOSURE_IS_BSDF_MICROFACET(type) ((type >= CLOSURE_BSDF_MICROFACET_GGX_ID && type <= CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ANISO_ID) ||\
-                                          (type >= CLOSURE_BSDF_REFRACTION_ID && type <= CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_ID))
+                                          (type >= CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID && type <= CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_ID) ||\
+                                          (type == CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_FRESNEL_ID))
 #define CLOSURE_IS_BSDF_OR_BSSRDF(type) (type <= CLOSURE_BSSRDF_BURLEY_ID)
 #define CLOSURE_IS_BSSRDF(type) (type >= CLOSURE_BSSRDF_CUBIC_ID && type <= CLOSURE_BSSRDF_BURLEY_ID)
 #define CLOSURE_IS_VOLUME(type) (type >= CLOSURE_VOLUME_ID && type <= CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID)

intern/cycles/util/util_math.h

@@ -518,6 +518,11 @@ ccl_device float safe_modulo(float a, float b)
 	return (b != 0.0f)? fmodf(a, b): 0.0f;
 }
 
+ccl_device_inline float sqr(float a)
+{
+	return a * a;
+}
+
 ccl_device_inline float beta(float x, float y)
 {
 #ifndef __KERNEL_OPENCL__