Cycles: Ashikhmin-Shirley anisotropic BSDF

* Ashikhmin-Shirley anisotropic BSDF was added as closure
* Anisotropic BSDF node now has two distributions

Reviewers: brecht, dingto

Differential Revision: https://developer.blender.org/D549

17 files changed, 315 insertions, 19 deletions

diff --git a/intern/cycles/app/cycles_xml.cpp b/intern/cycles/app/cycles_xml.cpp
index f50a952676f..915ef96a517 100644
--- a/intern/cycles/app/cycles_xml.cpp
+++ b/intern/cycles/app/cycles_xml.cpp
@@ -509,8 +509,10 @@ static void xml_read_shader_graph(const XMLReadState& state, Shader *shader, pug
 		else if(string_iequals(node.name(), "mapping")) {
 			snode = new MappingNode();
 		}
-		else if(string_iequals(node.name(), "ward_bsdf")) {
-			snode = new WardBsdfNode();
+		else if(string_iequals(node.name(), "anisotropic_bsdf")) {
+			AnisotropicBsdfNode *aniso = new AnisotropicBsdfNode();
+			xml_read_enum(&aniso->distribution, AnisotropicBsdfNode::distribution_enum, node, "distribution");
+			snode = aniso;
 		}
 		else if(string_iequals(node.name(), "diffuse_bsdf")) {
 			snode = new DiffuseBsdfNode();
diff --git a/intern/cycles/blender/blender_shader.cpp b/intern/cycles/blender/blender_shader.cpp
index 3b783d36b1e..226e7a76dda 100644
--- a/intern/cycles/blender/blender_shader.cpp
+++ b/intern/cycles/blender/blender_shader.cpp
@@ -318,7 +318,21 @@ static ShaderNode *add_node(Scene *scene, BL::BlendData b_data, BL::Scene b_scen
 		node = new HoldoutNode();
 	}
 	else if (b_node.is_a(&RNA_ShaderNodeBsdfAnisotropic)) {
-		node = new WardBsdfNode();
+		BL::ShaderNodeBsdfAnisotropic b_aniso_node(b_node);
+		AnisotropicBsdfNode *aniso = new AnisotropicBsdfNode();
+
+		switch (b_aniso_node.distribution())
+		{
+		case BL::ShaderNodeBsdfAnisotropic::distribution_ASHIKHMIN_SHIRLEY:
+			aniso->distribution = ustring("Ashikhmin-Shirley");
+			break;
+		case BL::ShaderNodeBsdfAnisotropic::distribution_WARD:
+		default:
+			aniso->distribution = ustring("Ward");
+			break;
+		}
+
+		node = aniso;
 	}
 	else if (b_node.is_a(&RNA_ShaderNodeBsdfDiffuse)) {
 		node = new DiffuseBsdfNode();
diff --git a/intern/cycles/kernel/CMakeLists.txt b/intern/cycles/kernel/CMakeLists.txt
index d34a045e4f3..6b6fcb10ba8 100644
--- a/intern/cycles/kernel/CMakeLists.txt
+++ b/intern/cycles/kernel/CMakeLists.txt
@@ -61,6 +61,7 @@ set(SRC_CLOSURE_HEADERS
 	closure/bsdf_transparent.h
 	closure/bsdf_util.h
 	closure/bsdf_ward.h
+	closure/bsdf_ashikhmin_shirley.h
 	closure/bsdf_westin.h
 	closure/bsdf_hair.h
 	closure/bssrdf.h
diff --git a/intern/cycles/kernel/closure/bsdf.h b/intern/cycles/kernel/closure/bsdf.h
index 24b54cd9d9e..371d0bfa8ea 100644
--- a/intern/cycles/kernel/closure/bsdf.h
+++ b/intern/cycles/kernel/closure/bsdf.h
@@ -25,6 +25,7 @@
 #include "../closure/bsdf_transparent.h"
 #ifdef __ANISOTROPIC__
 #include "../closure/bsdf_ward.h"
+#include "../closure/bsdf_ashikhmin_shirley.h"
 #endif
 #include "../closure/bsdf_westin.h"
 #include "../closure/bsdf_toon.h"
@@ -97,6 +98,10 @@ ccl_device int bsdf_sample(KernelGlobals *kg, const ShaderData *sd, const Shader
 			label = bsdf_ward_sample(sc, sd->Ng, sd->I, sd->dI.dx, sd->dI.dy, randu, randv,
 				eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
 			break;
+		case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID:
+			label = bsdf_ashikhmin_shirley_sample(sc, sd->Ng, sd->I, sd->dI.dx, sd->dI.dy, randu, randv,
+				eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
+			break;
 #endif
 		case CLOSURE_BSDF_ASHIKHMIN_VELVET_ID:
 			label = bsdf_ashikhmin_velvet_sample(sc, sd->Ng, sd->I, sd->dI.dx, sd->dI.dy, randu, randv,
@@ -189,6 +194,9 @@ ccl_device float3 bsdf_eval(KernelGlobals *kg, const ShaderData *sd, const Shade
 			case CLOSURE_BSDF_WARD_ID:
 				eval = bsdf_ward_eval_reflect(sc, sd->I, omega_in, pdf);
 				break;
+			case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID:
+				eval = bsdf_ashikhmin_shirley_eval_reflect(sc, sd->I, omega_in, pdf);
+				break;
 #endif
 			case CLOSURE_BSDF_ASHIKHMIN_VELVET_ID:
 				eval = bsdf_ashikhmin_velvet_eval_reflect(sc, sd->I, omega_in, pdf);
@@ -256,6 +264,9 @@ ccl_device float3 bsdf_eval(KernelGlobals *kg, const ShaderData *sd, const Shade
 			case CLOSURE_BSDF_WARD_ID:
 				eval = bsdf_ward_eval_transmit(sc, sd->I, omega_in, pdf);
 				break;
+			case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID:
+				eval = bsdf_ashikhmin_shirley_eval_transmit(sc, sd->I, omega_in, pdf);
+				break;
 #endif
 			case CLOSURE_BSDF_ASHIKHMIN_VELVET_ID:
 				eval = bsdf_ashikhmin_velvet_eval_transmit(sc, sd->I, omega_in, pdf);
@@ -341,6 +352,9 @@ ccl_device void bsdf_blur(KernelGlobals *kg, ShaderClosure *sc, float roughness)
 		case CLOSURE_BSDF_WARD_ID:
 			bsdf_ward_blur(sc, roughness);
 			break;
+		case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID:
+			bsdf_ashikhmin_shirley_blur(sc, roughness);
+			break;
 #endif
 		case CLOSURE_BSDF_ASHIKHMIN_VELVET_ID:
 			bsdf_ashikhmin_velvet_blur(sc, roughness);
diff --git a/intern/cycles/kernel/closure/bsdf_ashikhmin_shirley.h b/intern/cycles/kernel/closure/bsdf_ashikhmin_shirley.h
new file mode 100644
index 00000000000..ea5b610ae56
--- /dev/null
+++ b/intern/cycles/kernel/closure/bsdf_ashikhmin_shirley.h
@@ -0,0 +1,196 @@
+/*
+ * Copyright 2011-2013 Blender Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License
+ */
+
+#ifndef __BSDF_ASHIKHMIN_SHIRLEY_H__
+#define __BSDF_ASHIKHMIN_SHIRLEY_H__
+
+/*
+ASHIKHMIN SHIRLEY BSDF
+
+Implementation of
+Michael Ashikhmin and Peter Shirley: "An Anisotropic Phong BRDF Model" (2000)
+
+The Fresnel factor is missing to get a separable bsdf (intensity*color), as is
+the case with all other microfacet-based BSDF implementations in Cycles.
+
+Other than that, the implementation directly follows the paper.
+*/
+
+CCL_NAMESPACE_BEGIN
+
+
+ccl_device int bsdf_ashikhmin_shirley_setup(ShaderClosure *sc)
+{
+	sc->data0 = clamp(sc->data0, 1e-4f, 1.0f); /* store roughness. could already convert to exponent to save some cycles in eval, */
+	sc->data1 = clamp(sc->data1, 1e-4f, 1.0f); /* but this is more consistent with other bsdfs and shader_blur. */
+
+	sc->type = CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID;
+	return SD_BSDF | SD_BSDF_HAS_EVAL | SD_BSDF_GLOSSY;
+}
+
+ccl_device void bsdf_ashikhmin_shirley_blur(ShaderClosure *sc, float roughness)
+{
+	sc->data0 = fmaxf(roughness, sc->data0); /* clamp roughness */
+	sc->data1 = fmaxf(roughness, sc->data1);
+}
+
+ccl_device_inline float bsdf_ashikhmin_shirley_roughness_to_exponent(float roughness)
+{
+	return 2.0f / (roughness*roughness) - 2.0f;
+}
+
+ccl_device float3 bsdf_ashikhmin_shirley_eval_reflect(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf)
+{
+	float3 N = sc->N;
+	float3 T = sc->T;
+
+	float NdotI = dot(N, I);           /* in Cycles/OSL convention I is omega_out    */
+	float NdotO = dot(N, omega_in);    /* and consequently we use for O omaga_in ;)  */
+
+	float out = 0.0f;
+
+	if (NdotI > 0.0f && NdotO > 0.0f) {
+		NdotI = fmaxf(NdotI, 1e-6f);
+		NdotO = fmaxf(NdotO, 1e-6f);
+		float3 H = normalize(omega_in + I);
+		float HdotI = fmaxf(dot(H, I), 1e-6f);
+		float HdotN = fmaxf(dot(H, N), 1e-6f);
+
+		float pump = 1.0f / fmaxf(1e-6f, (HdotI*fmaxf(NdotO, NdotI))); /* pump from original paper (first derivative disc., but cancels the HdotI in the pdf nicely) */
+		/*float pump = 1.0f / fmaxf(1e-4f, ((NdotO + NdotI) * (NdotO*NdotI))); */ /* pump from d-brdf paper */
+
+		float n_x = bsdf_ashikhmin_shirley_roughness_to_exponent(sc->data0);
+		float n_y = bsdf_ashikhmin_shirley_roughness_to_exponent(sc->data1);
+
+		if (n_x == n_y) {  /* => isotropic case */
+			float e = n_x;
+			float lobe = powf(HdotN, e);
+			float norm = (n_x + 1.0f) / (8.0f * M_PI_F);
+
+			out = NdotO * norm * lobe * pump;
+			*pdf = norm * lobe / HdotI; /* this is p_h / 4(H.I)  (conversion from 'wh measure' to 'wi measure', eq. 8 in paper) */
+		}
+		else {             /* => ANisotropic case */
+			float3 X, Y;
+			make_orthonormals_tangent(N, T, &X, &Y);
+
+			float HdotX = dot(H, X);
+			float HdotY = dot(H, Y);
+			float e = (n_x * HdotX*HdotX + n_y * HdotY*HdotY) / (1.0f - HdotN*HdotN);
+			float lobe = powf(HdotN, e);
+			float norm = sqrtf((n_x + 1.0f)*(n_y + 1.0f)) / (8.0f * M_PI_F);
+			
+			out = NdotO * norm * lobe * pump;
+			*pdf = norm * lobe / HdotI;
+		}
+	}
+
+	return make_float3(out, out, out);
+}
+
+ccl_device float3 bsdf_ashikhmin_shirley_eval_transmit(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf)
+{
+	return make_float3(0.0f, 0.0f, 0.0f);
+}
+
+ccl_device_inline void bsdf_ashikhmin_shirley_sample_first_quadrant(float n_x, float n_y, float randu, float randv, float *phi, float *cos_theta)
+{
+	*phi = atanf(sqrtf((n_x + 1.0f) / (n_y + 1.0f)) * tanf(M_PI_2_F * randu));
+	float cos_phi = cosf(*phi);
+	float sin_phi = sinf(*phi);
+	*cos_theta = powf(randv, 1.0f / (n_x * cos_phi*cos_phi + n_y * sin_phi*sin_phi + 1.0f));
+}
+
+ccl_device int bsdf_ashikhmin_shirley_sample(const ShaderClosure *sc, float3 Ng, float3 I, float3 dIdx, float3 dIdy, float randu, float randv, float3 *eval, float3 *omega_in, float3 *domega_in_dx, float3 *domega_in_dy, float *pdf)
+{
+	float3 N = sc->N;
+	float3 T = sc->T;
+
+	float NdotI = dot(N, I);
+	if (NdotI > 0.0f) {
+
+		float n_x = bsdf_ashikhmin_shirley_roughness_to_exponent(sc->data0);
+		float n_y = bsdf_ashikhmin_shirley_roughness_to_exponent(sc->data1);
+
+		/* get x,y basis on the surface for anisotropy */
+		float3 X, Y;
+		make_orthonormals_tangent(N, T, &X, &Y);
+
+		/* sample spherical coords for h in tangent space */
+		float phi;
+		float cos_theta;
+		if (n_x == n_y) {  /* => simple isotropic sampling */
+			phi = M_2PI_F * randu;
+			cos_theta = powf(randv, 1.0f / (n_x + 1.0f));
+		}
+		else {             /* => more complex anisotropic sampling */
+			if (randu < 0.25f) {      /* first quadrant */
+				float remapped_randu = 4.0f * randu;
+				bsdf_ashikhmin_shirley_sample_first_quadrant(n_x, n_y, remapped_randu, randv, &phi, &cos_theta);
+			}
+			else if (randu < 0.5f) {  /* second quadrant */
+				float remapped_randu = 4.0f * (.5f - randu);
+				bsdf_ashikhmin_shirley_sample_first_quadrant(n_x, n_y, remapped_randu, randv, &phi, &cos_theta);
+				phi = M_PI_F - phi;
+			}
+			else if (randu < 0.75f) { /* third quadrant */
+				float remapped_randu = 4.0f * (randu - 0.5f);
+				bsdf_ashikhmin_shirley_sample_first_quadrant(n_x, n_y, remapped_randu, randv, &phi, &cos_theta);
+				phi = M_PI_F + phi;
+			}
+			else {                   /* fourth quadrant */
+				float remapped_randu = 4.0f * (1.0f - randu);
+				bsdf_ashikhmin_shirley_sample_first_quadrant(n_x, n_y, remapped_randu, randv, &phi, &cos_theta);
+				phi = 2.0f * M_PI_F - phi;
+			}
+		}
+
+		/* get half vector in tangent space */
+		float sin_theta = sqrtf(fmaxf(0.0f, 1.0f - cos_theta*cos_theta));
+		float cos_phi = cosf(phi);
+		float sin_phi = sinf(phi); /* no sqrt(1-cos^2) here b/c it causes artifacts */
+		float3 h = make_float3(
+			sin_theta * cos_phi,
+			sin_theta * sin_phi,
+			cos_theta
+			);
+
+		/* half vector to world space */
+		float3 H = h.x*X + h.y*Y + h.z*N;
+		float HdotI = dot(H, I);
+		if (HdotI < 0.0f) H = -H;
+
+		/* reflect I on H to get omega_in */
+		*omega_in = -I + (2.0f * HdotI) * H;
+
+		/* leave the rest to eval_reflect */
+		/* (could maybe optimize a few things by manual inlining, but I doubt it would make much difference) */
+		*eval = bsdf_ashikhmin_shirley_eval_reflect(sc, I, *omega_in, pdf);
+
+#ifdef __RAY_DIFFERENTIALS__
+		/* just do the reflection thing for now */
+		*domega_in_dx = (2.0f * dot(N, dIdx)) * N - dIdx;
+		*domega_in_dy = (2.0f * dot(N, dIdy)) * N - dIdy;
+#endif
+	}
+
+	return LABEL_REFLECT | LABEL_GLOSSY;
+}
+
+
+CCL_NAMESPACE_END
+
+#endif /* __BSDF_ASHIKHMIN_SHIRLEY_H__ */
diff --git a/intern/cycles/kernel/osl/osl_closures.cpp b/intern/cycles/kernel/osl/osl_closures.cpp
index a96c0e2b1fb..9a1819ca116 100644
--- a/intern/cycles/kernel/osl/osl_closures.cpp
+++ b/intern/cycles/kernel/osl/osl_closures.cpp
@@ -52,6 +52,7 @@
 #include "closure/bsdf_refraction.h"
 #include "closure/bsdf_transparent.h"
 #include "closure/bsdf_ward.h"
+#include "closure/bsdf_ashikhmin_shirley.h"
 #include "closure/bsdf_westin.h"
 #include "closure/bsdf_toon.h"
 #include "closure/bsdf_hair.h"
@@ -110,6 +111,13 @@ BSDF_CLOSURE_CLASS_BEGIN(Ward, ward, ward, LABEL_GLOSSY)
 	CLOSURE_FLOAT_PARAM(WardClosure, sc.data1),
 BSDF_CLOSURE_CLASS_END(Ward, ward)
 
+BSDF_CLOSURE_CLASS_BEGIN(AshikhminShirley, ashikhmin_shirley, ashikhmin_shirley, LABEL_GLOSSY)
+	CLOSURE_FLOAT3_PARAM(AshikhminShirleyClosure, sc.N),
+	CLOSURE_FLOAT3_PARAM(AshikhminShirleyClosure, sc.T),
+	CLOSURE_FLOAT_PARAM(AshikhminShirleyClosure, sc.data0),
+	CLOSURE_FLOAT_PARAM(AshikhminShirleyClosure, sc.data1),
+BSDF_CLOSURE_CLASS_END(AshikhminShirley, ashikhmin_shirley)
+
 BSDF_CLOSURE_CLASS_BEGIN(DiffuseToon, diffuse_toon, diffuse_toon, LABEL_DIFFUSE)
 	CLOSURE_FLOAT3_PARAM(DiffuseToonClosure, sc.N),
 	CLOSURE_FLOAT_PARAM(DiffuseToonClosure, sc.data0),
@@ -218,6 +226,8 @@ void OSLShader::register_closures(OSLShadingSystem *ss_)
 		bsdf_microfacet_beckmann_refraction_params(), bsdf_microfacet_beckmann_refraction_prepare);
 	register_closure(ss, "ward", id++,
 		bsdf_ward_params(), bsdf_ward_prepare);
+	register_closure(ss, "ashikhmin_shirley", id++,
+		bsdf_ashikhmin_shirley_params(), bsdf_ashikhmin_shirley_prepare);
 	register_closure(ss, "ashikhmin_velvet", id++,
 		bsdf_ashikhmin_velvet_params(), bsdf_ashikhmin_velvet_prepare);
 	register_closure(ss, "diffuse_toon", id++,
diff --git a/intern/cycles/kernel/shaders/CMakeLists.txt b/intern/cycles/kernel/shaders/CMakeLists.txt
index b164c2a03f7..0b735ede701 100644
--- a/intern/cycles/kernel/shaders/CMakeLists.txt
+++ b/intern/cycles/kernel/shaders/CMakeLists.txt
@@ -4,6 +4,7 @@
 set(SRC_OSL
 	node_add_closure.osl
 	node_ambient_occlusion.osl
+	node_anisotropic_bsdf.osl
 	node_attribute.osl
 	node_background.osl
 	node_brick_texture.osl
@@ -73,7 +74,6 @@ set(SRC_OSL
 	node_vector_transform.osl
 	node_velvet_bsdf.osl
 	node_voronoi_texture.osl
-	node_ward_bsdf.osl
 	node_wavelength.osl
 	node_blackbody.osl
 	node_wave_texture.osl
diff --git a/intern/cycles/kernel/shaders/node_ward_bsdf.osl b/intern/cycles/kernel/shaders/node_anisotropic_bsdf.osl
index 2d360d594f2..3ecf5b46bef 100644
--- a/intern/cycles/kernel/shaders/node_ward_bsdf.osl
+++ b/intern/cycles/kernel/shaders/node_anisotropic_bsdf.osl
@@ -16,8 +16,9 @@
 
 #include "stdosl.h"
 
-shader node_ward_bsdf(
+shader node_anisotropic_bsdf(
 	color Color = 0.0,
+	string distribution = "Ward",
 	float Roughness = 0.0,
 	float Anisotropy = 0.0,
 	float Rotation = 0.0,
@@ -44,6 +45,9 @@ shader node_ward_bsdf(
 		RoughnessV = Roughness / (1.0 - aniso);
 	}
 
-	BSDF = Color * ward(Normal, T, RoughnessU, RoughnessV);
+	if (distribution == "Ashikhmin-Shirley")
+		BSDF = Color * ashikhmin_shirley(Normal, T, RoughnessU, RoughnessV);
+	else
+		BSDF = Color * ward(Normal, T, RoughnessU, RoughnessV);
 }
 
diff --git a/intern/cycles/kernel/shaders/stdosl.h b/intern/cycles/kernel/shaders/stdosl.h
index 6f824ea8ebd..20ee4a3df32 100644
--- a/intern/cycles/kernel/shaders/stdosl.h
+++ b/intern/cycles/kernel/shaders/stdosl.h
@@ -486,6 +486,7 @@ closure color microfacet_ggx(normal N, float ag) BUILTIN;
 closure color microfacet_ggx_refraction(normal N, float ag, float eta) BUILTIN;
 closure color microfacet_beckmann(normal N, float ab) BUILTIN;
 closure color microfacet_beckmann_refraction(normal N, float ab, float eta) BUILTIN;
+closure color ashikhmin_shirley(normal N, vector T,float ax, float ay) BUILTIN;
 closure color ward(normal N, vector T,float ax, float ay) BUILTIN;
 closure color ashikhmin_velvet(normal N, float sigma) BUILTIN;
 closure color emission() BUILTIN;
diff --git a/intern/cycles/kernel/svm/svm_closure.h b/intern/cycles/kernel/svm/svm_closure.h
index a7982c64c49..d68b9371061 100644
--- a/intern/cycles/kernel/svm/svm_closure.h
+++ b/intern/cycles/kernel/svm/svm_closure.h
@@ -269,7 +269,8 @@ ccl_device void svm_node_closure_bsdf(KernelGlobals *kg, ShaderData *sd, float *
 
 			break;
 		}
-		case CLOSURE_BSDF_WARD_ID: {
+		case CLOSURE_BSDF_WARD_ID:
+		case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID: {
 #ifdef __CAUSTICS_TRICKS__
 			if(kernel_data.integrator.no_caustics && (path_flag & PATH_RAY_DIFFUSE))
 				break;
@@ -301,7 +302,11 @@ ccl_device void svm_node_closure_bsdf(KernelGlobals *kg, ShaderData *sd, float *
 					sc->data1 = roughness/(1.0f - anisotropy);
 				}
 
-				sd->flag |= bsdf_ward_setup(sc);
+				if (type == CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID)
+					sd->flag |= bsdf_ashikhmin_shirley_setup(sc);
+				else
+					sd->flag |= bsdf_ward_setup(sc);
+
 #else
 				sd->flag |= bsdf_diffuse_setup(sc);
 #endif
diff --git a/intern/cycles/kernel/svm/svm_types.h b/intern/cycles/kernel/svm/svm_types.h
index 20c799e1805..87c56b3ea82 100644
--- a/intern/cycles/kernel/svm/svm_types.h
+++ b/intern/cycles/kernel/svm/svm_types.h
@@ -358,6 +358,7 @@ typedef enum ClosureType {
 	CLOSURE_BSDF_MICROFACET_GGX_ID,
 	CLOSURE_BSDF_MICROFACET_BECKMANN_ID,
 	CLOSURE_BSDF_WARD_ID,
+	CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID,
 	CLOSURE_BSDF_ASHIKHMIN_VELVET_ID,
 	CLOSURE_BSDF_WESTIN_BACKSCATTER_ID,
 	CLOSURE_BSDF_PHONG_RAMP_ID,
@@ -403,7 +404,7 @@ typedef enum ClosureType {
 #define CLOSURE_IS_BSDF_GLOSSY(type) (type >= CLOSURE_BSDF_GLOSSY_ID && type <= CLOSURE_BSDF_HAIR_REFLECTION_ID)
 #define CLOSURE_IS_BSDF_TRANSMISSION(type) (type >= CLOSURE_BSDF_TRANSMISSION_ID && type <= CLOSURE_BSDF_HAIR_TRANSMISSION_ID)
 #define CLOSURE_IS_BSDF_BSSRDF(type) (type == CLOSURE_BSDF_BSSRDF_ID)
-#define CLOSURE_IS_BSDF_ANISOTROPIC(type) (type == CLOSURE_BSDF_WARD_ID)
+#define CLOSURE_IS_BSDF_ANISOTROPIC(type) (type >= CLOSURE_BSDF_WARD_ID && type <= CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID)
 #define CLOSURE_IS_BSDF_OR_BSSRDF(type) (type <= CLOSURE_BSSRDF_GAUSSIAN_ID)
 #define CLOSURE_IS_BSSRDF(type) (type >= CLOSURE_BSSRDF_CUBIC_ID && type <= CLOSURE_BSSRDF_GAUSSIAN_ID)
 #define CLOSURE_IS_VOLUME(type) (type >= CLOSURE_VOLUME_ID && type <= CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID)
diff --git a/intern/cycles/render/nodes.cpp b/intern/cycles/render/nodes.cpp
index a38de8a5cec..8976f958b58 100644
--- a/intern/cycles/render/nodes.cpp
+++ b/intern/cycles/render/nodes.cpp
@@ -1583,11 +1583,23 @@ void BsdfNode::compile(OSLCompiler& compiler)
 	assert(0);
 }
 
-/* Ward BSDF Closure */
+/* Anisotropic BSDF Closure */
 
-WardBsdfNode::WardBsdfNode()
+static ShaderEnum anisotropic_distribution_init()
 {
-	closure = CLOSURE_BSDF_WARD_ID;
+	ShaderEnum enm;
+
+	enm.insert("Ward",              CLOSURE_BSDF_WARD_ID);
+	enm.insert("Ashikhmin-Shirley", CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID);
+
+	return enm;
+}
+
+ShaderEnum AnisotropicBsdfNode::distribution_enum = anisotropic_distribution_init();
+
+AnisotropicBsdfNode::AnisotropicBsdfNode()
+{
+	distribution = ustring("Ward");
 
 	add_input("Tangent", SHADER_SOCKET_VECTOR, ShaderInput::TANGENT);
 
@@ -1596,7 +1608,7 @@ WardBsdfNode::WardBsdfNode()
 	add_input("Rotation", SHADER_SOCKET_FLOAT, 0.0f);
 }
 
-void WardBsdfNode::attributes(Shader *shader, AttributeRequestSet *attributes)
+void AnisotropicBsdfNode::attributes(Shader *shader, AttributeRequestSet *attributes)
 {
 	if(shader->has_surface) {
 		ShaderInput *tangent_in = input("Tangent");
@@ -1608,14 +1620,17 @@ void WardBsdfNode::attributes(Shader *shader, AttributeRequestSet *attributes)
 	ShaderNode::attributes(shader, attributes);
 }
 
-void WardBsdfNode::compile(SVMCompiler& compiler)
+void AnisotropicBsdfNode::compile(SVMCompiler& compiler)
 {
+	closure = (ClosureType)distribution_enum[distribution];
+
 	BsdfNode::compile(compiler, input("Roughness"), input("Anisotropy"), input("Rotation"));
 }
 
-void WardBsdfNode::compile(OSLCompiler& compiler)
+void AnisotropicBsdfNode::compile(OSLCompiler& compiler)
 {
-	compiler.add(this, "node_ward_bsdf");
+	compiler.parameter("distribution", distribution);
+	compiler.add(this, "node_anisotropic_bsdf");
 }
 
 /* Glossy BSDF Closure */
diff --git a/intern/cycles/render/nodes.h b/intern/cycles/render/nodes.h
index cf89bdadaa2..31b6f4e50c4 100644
--- a/intern/cycles/render/nodes.h
+++ b/intern/cycles/render/nodes.h
@@ -218,9 +218,13 @@ public:
 	bool scattering;
 };
 
-class WardBsdfNode : public BsdfNode {
+class AnisotropicBsdfNode : public BsdfNode {
 public:
-	SHADER_NODE_CLASS(WardBsdfNode)
+	SHADER_NODE_CLASS(AnisotropicBsdfNode)
+
+	ustring distribution;
+	static ShaderEnum distribution_enum;
+
 	void attributes(Shader *shader, AttributeRequestSet *attributes);
 };
 
diff --git a/source/blender/editors/space_node/drawnode.c b/source/blender/editors/space_node/drawnode.c
index 953777ff329..4e709046f45 100644
--- a/source/blender/editors/space_node/drawnode.c
+++ b/source/blender/editors/space_node/drawnode.c
@@ -930,6 +930,11 @@ static void node_shader_buts_glossy(uiLayout *layout, bContext *UNUSED(C), Point
 	uiItemR(layout, ptr, "distribution", 0, "", ICON_NONE);
 }
 
+static void node_shader_buts_anisotropic(uiLayout *layout, bContext *UNUSED(C), PointerRNA *ptr)
+{
+	uiItemR(layout, ptr, "distribution", 0, "", ICON_NONE);
+}
+
 static void node_shader_buts_subsurface(uiLayout *layout, bContext *C, PointerRNA *ptr)
 {
 	/* SSS does not work on GPU yet */
@@ -1096,6 +1101,9 @@ static void node_shader_set_butfunc(bNodeType *ntype)
 		case SH_NODE_BSDF_REFRACTION:
 			ntype->draw_buttons = node_shader_buts_glossy;
 			break;
+		case SH_NODE_BSDF_ANISOTROPIC:
+			ntype->draw_buttons = node_shader_buts_anisotropic;
+			break;
 		case SH_NODE_SUBSURFACE_SCATTERING:
 			ntype->draw_buttons = node_shader_buts_subsurface;
 			break;
diff --git a/source/blender/makesdna/DNA_node_types.h b/source/blender/makesdna/DNA_node_types.h
index e13d53934cb..2241803610c 100644
--- a/source/blender/makesdna/DNA_node_types.h
+++ b/source/blender/makesdna/DNA_node_types.h
@@ -873,6 +873,10 @@ typedef struct NodeShaderUVMap {
 #define CMP_NODE_CHANNEL_MATTE_CS_YUV	3
 #define CMP_NODE_CHANNEL_MATTE_CS_YCC	4
 
+/* anisotropic distributions */
+#define SHD_ANISOTROPIC_WARD               0
+#define SHD_ANISOTROPIC_ASHIKHMIN_SHIRLEY  1
+
 /* glossy distributions */
 #define SHD_GLOSSY_BECKMANN	0
 #define SHD_GLOSSY_SHARP	1
diff --git a/source/blender/makesrna/intern/rna_nodetree.c b/source/blender/makesrna/intern/rna_nodetree.c
index c39d3826d8b..b1a2f12d781 100644
--- a/source/blender/makesrna/intern/rna_nodetree.c
+++ b/source/blender/makesrna/intern/rna_nodetree.c
@@ -2952,6 +2952,12 @@ static EnumPropertyItem node_glossy_items[] = {
 	{0, NULL, 0, NULL, NULL}
 };
 
+static EnumPropertyItem node_anisotropic_items[] = {
+	{SHD_ANISOTROPIC_WARD,              "WARD",              0, "Ward",              ""},
+	{SHD_ANISOTROPIC_ASHIKHMIN_SHIRLEY, "ASHIKHMIN_SHIRLEY", 0, "Ashikhmin-Shirley", ""},
+	{0, NULL, 0, NULL, NULL}
+};
+
 static EnumPropertyItem node_toon_items[] = {
 	{SHD_TOON_DIFFUSE,    "DIFFUSE",  0, "Diffuse", ""},
 	{SHD_TOON_GLOSSY,     "GLOSSY",   0, "Glossy",  ""},
@@ -3699,6 +3705,17 @@ static void def_glossy(StructRNA *srna)
 	RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_Node_update");
 }
 
+static void def_anisotropic(StructRNA *srna)
+{
+	PropertyRNA *prop;
+
+	prop = RNA_def_property(srna, "distribution", PROP_ENUM, PROP_NONE);
+	RNA_def_property_enum_sdna(prop, NULL, "custom1");
+	RNA_def_property_enum_items(prop, node_anisotropic_items);
+	RNA_def_property_ui_text(prop, "Distribution", "");
+	RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_Node_update");
+}
+
 static void def_toon(StructRNA *srna)
 {
 	PropertyRNA *prop;
diff --git a/source/blender/nodes/NOD_static_types.h b/source/blender/nodes/NOD_static_types.h
index 3e5de09ff6c..08dffd0ac92 100644
--- a/source/blender/nodes/NOD_static_types.h
+++ b/source/blender/nodes/NOD_static_types.h
@@ -77,7 +77,7 @@ DefNode( ShaderNode,     SH_NODE_ATTRIBUTE,          def_sh_attribute,       "AT
 DefNode( ShaderNode,     SH_NODE_AMBIENT_OCCLUSION,  0,                      "AMBIENT_OCCLUSION",  AmbientOcclusion, "Ambient Occlusion", ""       )
 DefNode( ShaderNode,     SH_NODE_BACKGROUND,         0,                      "BACKGROUND",         Background,       "Background",        ""       )
 DefNode( ShaderNode,     SH_NODE_HOLDOUT,            0,                      "HOLDOUT",            Holdout,          "Holdout",           ""       )
-DefNode( ShaderNode,     SH_NODE_BSDF_ANISOTROPIC,   0,                      "BSDF_ANISOTROPIC",   BsdfAnisotropic,  "Anisotropic BSDF",  ""       )
+DefNode( ShaderNode,     SH_NODE_BSDF_ANISOTROPIC,   def_anisotropic,        "BSDF_ANISOTROPIC",   BsdfAnisotropic,  "Anisotropic BSDF",  ""       )
 DefNode( ShaderNode,     SH_NODE_BSDF_DIFFUSE,       0,                      "BSDF_DIFFUSE",       BsdfDiffuse,      "Diffuse BSDF",      ""       )
 DefNode( ShaderNode,     SH_NODE_BSDF_GLOSSY,        def_glossy,             "BSDF_GLOSSY",        BsdfGlossy,       "Glossy BSDF",       ""       )
 DefNode( ShaderNode,     SH_NODE_BSDF_GLASS,         def_glossy,             "BSDF_GLASS",         BsdfGlass,        "Glass BSDF",        ""       )