Cycles: add random walk subsurface scattering to Principled BSDF.

Differential Revision: https://developer.blender.org/D3054

6 files changed, 28 insertions, 9 deletions

diff --git a/intern/cycles/kernel/closure/bssrdf.h b/intern/cycles/kernel/closure/bssrdf.h
index 790368ee888..8578767b07e 100644
--- a/intern/cycles/kernel/closure/bssrdf.h
+++ b/intern/cycles/kernel/closure/bssrdf.h
@@ -373,7 +373,9 @@ ccl_device int bssrdf_setup(ShaderData *sd, Bssrdf *bssrdf, ClosureType type)
 	if(bssrdf_channels < 3) {
 		/* Add diffuse BSDF if any radius too small. */
 #ifdef __PRINCIPLED__
-		if(type == CLOSURE_BSSRDF_PRINCIPLED_ID) {
+		if(type == CLOSURE_BSSRDF_PRINCIPLED_ID ||
+		   type == CLOSURE_BSSRDF_PRINCIPLED_RANDOM_WALK_ID)
+		{
 			float roughness = bssrdf->roughness;
 			float3 N = bssrdf->N;
 
@@ -409,7 +411,8 @@ ccl_device int bssrdf_setup(ShaderData *sd, Bssrdf *bssrdf, ClosureType type)
 
 		if(type == CLOSURE_BSSRDF_BURLEY_ID ||
 		   type == CLOSURE_BSSRDF_PRINCIPLED_ID ||
-		   type == CLOSURE_BSSRDF_RANDOM_WALK_ID)
+		   type == CLOSURE_BSSRDF_RANDOM_WALK_ID ||
+		   type == CLOSURE_BSSRDF_PRINCIPLED_RANDOM_WALK_ID)
 		{
 			bssrdf_burley_setup(bssrdf);
 		}
diff --git a/intern/cycles/kernel/kernel_subsurface.h b/intern/cycles/kernel/kernel_subsurface.h
index a0dba7e1386..80dda31c61e 100644
--- a/intern/cycles/kernel/kernel_subsurface.h
+++ b/intern/cycles/kernel/kernel_subsurface.h
@@ -78,7 +78,9 @@ ccl_device void subsurface_scatter_setup_diffuse_bsdf(KernelGlobals *kg, ShaderD
 	if(hit) {
 		Bssrdf *bssrdf = (Bssrdf *)sc;
 #ifdef __PRINCIPLED__
-		if(bssrdf->type == CLOSURE_BSSRDF_PRINCIPLED_ID) {
+		if(bssrdf->type == CLOSURE_BSSRDF_PRINCIPLED_ID ||
+		   bssrdf->type == CLOSURE_BSSRDF_PRINCIPLED_RANDOM_WALK_ID)
+		{
 			PrincipledDiffuseBsdf *bsdf = (PrincipledDiffuseBsdf*)bsdf_alloc(sd, sizeof(PrincipledDiffuseBsdf), weight);
 
 			if(bsdf) {
diff --git a/intern/cycles/kernel/osl/osl_bssrdf.cpp b/intern/cycles/kernel/osl/osl_bssrdf.cpp
index 907afe7d17a..da7368bbc61 100644
--- a/intern/cycles/kernel/osl/osl_bssrdf.cpp
+++ b/intern/cycles/kernel/osl/osl_bssrdf.cpp
@@ -53,6 +53,7 @@ static ustring u_gaussian("gaussian");
 static ustring u_burley("burley");
 static ustring u_principled("principled");
 static ustring u_random_walk("random_walk");
+static ustring u_principled_random_walk("principled_random_walk");
 
 class CBSSRDFClosure : public CClosurePrimitive {
 public:
@@ -83,6 +84,9 @@ public:
 		else if (method == u_random_walk) {
 			alloc(sd, path_flag, weight, CLOSURE_BSSRDF_RANDOM_WALK_ID);
 		}
+		else if (method == u_principled_random_walk) {
+			alloc(sd, path_flag, weight, CLOSURE_BSSRDF_PRINCIPLED_RANDOM_WALK_ID);
+		}
 	}
 
 	void alloc(ShaderData *sd, int path_flag, float3 weight, ClosureType type)
diff --git a/intern/cycles/kernel/shaders/node_principled_bsdf.osl b/intern/cycles/kernel/shaders/node_principled_bsdf.osl
index 0e31dcedee4..fc0a1c894da 100644
--- a/intern/cycles/kernel/shaders/node_principled_bsdf.osl
+++ b/intern/cycles/kernel/shaders/node_principled_bsdf.osl
@@ -19,6 +19,7 @@
 
 shader node_principled_bsdf(
 	string distribution = "Multiscatter GGX",
+	string subsurface_method = "burley",
 	color BaseColor = color(0.8, 0.8, 0.8),
 	float Subsurface = 0.0,
 	vector SubsurfaceRadius = vector(1.0, 1.0, 1.0),
@@ -58,8 +59,14 @@ shader node_principled_bsdf(
 	if (diffuse_weight > 1e-5) {
 		if (Subsurface > 1e-5) {
 			color mixed_ss_base_color = SubsurfaceColor * Subsurface + BaseColor * (1.0 - Subsurface);
-			BSDF = mixed_ss_base_color * bssrdf("principled", Normal, Subsurface * SubsurfaceRadius, SubsurfaceColor, "roughness", Roughness);
-		} else {
+			if (subsurface_method == "burley") {
+				BSDF = mixed_ss_base_color * bssrdf("principled", Normal, Subsurface * SubsurfaceRadius, SubsurfaceColor, "roughness", Roughness);
+			}
+			else {
+				BSDF = mixed_ss_base_color * bssrdf("principled_random_walk", Normal, Subsurface * SubsurfaceRadius, SubsurfaceColor, "roughness", Roughness);
+			}
+		}
+		else {
 			BSDF = BaseColor * principled_diffuse(Normal, Roughness);
 		}
 
diff --git a/intern/cycles/kernel/svm/svm_closure.h b/intern/cycles/kernel/svm/svm_closure.h
index f013dc396d0..fa43e1b60d0 100644
--- a/intern/cycles/kernel/svm/svm_closure.h
+++ b/intern/cycles/kernel/svm/svm_closure.h
@@ -114,7 +114,8 @@ ccl_device void svm_node_closure_bsdf(KernelGlobals *kg, ShaderData *sd, float *
 			float transmission_roughness = stack_load_float(stack, transmission_roughness_offset);
 			float eta = fmaxf(stack_load_float(stack, eta_offset), 1e-5f);
 
-			ClosureType distribution = stack_valid(data_node2.y) ? (ClosureType) data_node2.y : CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_ID;
+			ClosureType distribution = (ClosureType) data_node2.y;
+			ClosureType subsurface_method = (ClosureType) data_node2.z;
 
 			/* rotate tangent */
 			if(anisotropic_rotation != 0.0f)
@@ -193,7 +194,7 @@ ccl_device void svm_node_closure_bsdf(KernelGlobals *kg, ShaderData *sd, float *
 						bssrdf->roughness = roughness;
 
 						/* setup bsdf */
-						sd->flag |= bssrdf_setup(sd, bssrdf, (ClosureType)CLOSURE_BSSRDF_PRINCIPLED_ID);
+						sd->flag |= bssrdf_setup(sd, bssrdf, subsurface_method);
 					}
 				}
 			}
@@ -781,6 +782,7 @@ ccl_device void svm_node_closure_bsdf(KernelGlobals *kg, ShaderData *sd, float *
 				bssrdf->texture_blur = param2;
 				bssrdf->sharpness = stack_load_float(stack, data_node.w);
 				bssrdf->N = N;
+				bssrdf->roughness = 0.0f;
 				sd->flag |= bssrdf_setup(sd, bssrdf, (ClosureType)type);
 			}
 
diff --git a/intern/cycles/kernel/svm/svm_types.h b/intern/cycles/kernel/svm/svm_types.h
index 9a87b4ee358..c0ce0f52cd0 100644
--- a/intern/cycles/kernel/svm/svm_types.h
+++ b/intern/cycles/kernel/svm/svm_types.h
@@ -447,6 +447,7 @@ typedef enum ClosureType {
 	CLOSURE_BSSRDF_PRINCIPLED_ID,
 	CLOSURE_BSSRDF_BURLEY_ID,
 	CLOSURE_BSSRDF_RANDOM_WALK_ID,
+	CLOSURE_BSSRDF_PRINCIPLED_RANDOM_WALK_ID,
 
 	/* Other */
 	CLOSURE_HOLDOUT_ID,
@@ -478,8 +479,8 @@ typedef enum ClosureType {
 #define CLOSURE_IS_BSDF_MICROFACET(type) ((type >= CLOSURE_BSDF_MICROFACET_GGX_ID && type <= CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ANISO_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_RANDOM_WALK_ID)
-#define CLOSURE_IS_BSSRDF(type) (type >= CLOSURE_BSSRDF_CUBIC_ID && type <= CLOSURE_BSSRDF_RANDOM_WALK_ID)
+#define CLOSURE_IS_BSDF_OR_BSSRDF(type) (type <= CLOSURE_BSSRDF_PRINCIPLED_RANDOM_WALK_ID)
+#define CLOSURE_IS_BSSRDF(type) (type >= CLOSURE_BSSRDF_CUBIC_ID && type <= CLOSURE_BSSRDF_PRINCIPLED_RANDOM_WALK_ID)
 #define CLOSURE_IS_DISK_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)
 #define CLOSURE_IS_VOLUME_SCATTER(type) (type == CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID)