Cycles Hair: Two basic bair shaders added

A new hair bsdf node, with two closure options, is added. These closures allow the generation of the reflective and transmission components of hair. The node allows control of the highlight colour, roughness and angular shift.

Llimitations include:
-No glint or fresnel adjustments.
-The 'offset' is un-used when triangle primitives are used.

2 files changed, 304 insertions, 0 deletions

diff --git a/intern/cycles/kernel/closure/bsdf.h b/intern/cycles/kernel/closure/bsdf.h
index d81bbebd5a8..86fea48760f 100644
--- a/intern/cycles/kernel/closure/bsdf.h
+++ b/intern/cycles/kernel/closure/bsdf.h
@@ -28,6 +28,7 @@
 #endif
 #include "../closure/bsdf_westin.h"
 #include "../closure/bsdf_toon.h"
+#include "../closure/bsdf_hair.h"
 #ifdef __SUBSURFACE__
 #include "../closure/bssrdf.h"
 #endif
@@ -114,6 +115,14 @@ __device int bsdf_sample(KernelGlobals *kg, const ShaderData *sd, const ShaderCl
 			label = bsdf_westin_sheen_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_HAIR_REFLECTION_ID:
+			label = bsdf_hair_reflection_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_HAIR_TRANSMISSION_ID:
+			label = bsdf_hair_transmission_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
 		default:
 			label = LABEL_NONE;
@@ -188,6 +197,12 @@ __device float3 bsdf_eval(KernelGlobals *kg, const ShaderData *sd, const ShaderC
 			case CLOSURE_BSDF_WESTIN_SHEEN_ID:
 				eval = bsdf_westin_sheen_eval_reflect(sc, sd->I, omega_in, pdf);
 				break;
+			case CLOSURE_BSDF_HAIR_REFLECTION_ID:
+				eval = bsdf_hair_reflection_eval_reflect(sc, sd->I, omega_in, pdf);
+				break;
+			case CLOSURE_BSDF_HAIR_TRANSMISSION_ID:
+				eval = bsdf_hair_transmission_eval_reflect(sc, sd->I, omega_in, pdf);
+				break;
 #endif
 			default:
 				eval = make_float3(0.0f, 0.0f, 0.0f);
@@ -244,6 +259,12 @@ __device float3 bsdf_eval(KernelGlobals *kg, const ShaderData *sd, const ShaderC
 			case CLOSURE_BSDF_WESTIN_SHEEN_ID:
 				eval = bsdf_westin_sheen_eval_transmit(sc, sd->I, omega_in, pdf);
 				break;
+			case CLOSURE_BSDF_HAIR_REFLECTION_ID:
+				eval = bsdf_hair_reflection_eval_transmit(sc, sd->I, omega_in, pdf);
+				break;
+			case CLOSURE_BSDF_HAIR_TRANSMISSION_ID:
+				eval = bsdf_hair_transmission_eval_transmit(sc, sd->I, omega_in, pdf);
+				break;
 #endif
 			default:
 				eval = make_float3(0.0f, 0.0f, 0.0f);
@@ -318,6 +339,10 @@ __device void bsdf_blur(KernelGlobals *kg, ShaderClosure *sc, float roughness)
 		case CLOSURE_BSDF_WESTIN_SHEEN_ID:
 			bsdf_westin_sheen_blur(sc, roughness);
 			break;
+		case CLOSURE_BSDF_HAIR_REFLECTION_ID:
+		case CLOSURE_BSDF_HAIR_TRANSMISSION_ID:
+			bsdf_hair_reflection_blur(sc, roughness);
+			break;
 #endif
 		default:
 			break;
diff --git a/intern/cycles/kernel/closure/bsdf_hair.h b/intern/cycles/kernel/closure/bsdf_hair.h
new file mode 100644
index 00000000000..5791598459c
--- /dev/null
+++ b/intern/cycles/kernel/closure/bsdf_hair.h
@@ -0,0 +1,279 @@
+/*
+ * Adapted from Open Shading Language with this license:
+ *
+ * Copyright (c) 2009-2010 Sony Pictures Imageworks Inc., et al.
+ * All Rights Reserved.
+ *
+ * Modifications Copyright 2011, Blender Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ * * Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ * * Neither the name of Sony Pictures Imageworks nor the names of its
+ *   contributors may be used to endorse or promote products derived from
+ *   this software without specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef __BSDF_HAIR_H__
+#define __BSDF_HAIR_H__
+
+CCL_NAMESPACE_BEGIN
+
+
+__device void bsdf_hair_reflection_blur(ShaderClosure *sc, float roughness)
+{
+}
+
+__device void bsdf_hair_transmission_blur(ShaderClosure *sc, float roughness)
+{
+}
+
+__device int bsdf_hair_reflection_setup(ShaderClosure *sc)
+{
+	sc->type = CLOSURE_BSDF_HAIR_REFLECTION_ID;
+	sc->data0 = clamp(sc->data0, 0.001f,1.0f);
+	sc->data1 = clamp(sc->data1, 0.001f,1.0f);
+	return SD_BSDF|SD_BSDF_HAS_EVAL|SD_BSDF_GLOSSY;
+}
+
+__device int bsdf_hair_transmission_setup(ShaderClosure *sc)
+{
+	sc->type = CLOSURE_BSDF_HAIR_TRANSMISSION_ID;
+	sc->data0 = clamp(sc->data0, 0.001f,1.0f);
+	sc->data1 = clamp(sc->data1, 0.001f,1.0f);
+	return SD_BSDF|SD_BSDF_HAS_EVAL|SD_BSDF_GLOSSY;
+}
+
+__device float3 bsdf_hair_reflection_eval_reflect(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf)
+{
+#ifdef __HAIR__
+	float offset = sc->offset;
+	float3 Tg = sc->T;
+#else
+	float offset = 0.0f;
+	float3 Tg = make_float3(1.0f,0.0f,0.0f);
+#endif
+	float roughness1 = sc->data0;
+	float roughness2 = sc->data1;
+
+	float Iz = dot(Tg, I);
+	float3 locy = normalize(I - Tg * Iz);
+	float3 locx = cross(locy, Tg);
+
+	float theta_r = M_PI_2_F - safe_acosf(Iz);
+
+	float omega_in_z = dot(Tg, omega_in);
+	float3 omega_in_y = normalize(omega_in - Tg * omega_in_z);
+
+	float theta_i = M_PI_2_F - safe_acosf(omega_in_z);
+	float cosphi_i = dot(omega_in_y, locy);
+
+	if(M_PI_2_F - fabsf(theta_i) < 0.001f || cosphi_i < 0.0f){
+		*pdf = 0.0f;
+		return make_float3(*pdf, *pdf, *pdf);
+	}
+
+	float phi_i = safe_acosf(cosphi_i) / roughness2;
+	phi_i = fabsf(phi_i) < M_PI_F ? phi_i : M_PI_F;
+	float costheta_i = cosf(theta_i);
+
+	float a_R = atan2f(((M_PI_2_F + theta_r) * 0.5f - offset) / roughness1, 1.0f);
+	float b_R = atan2f(((-M_PI_2_F + theta_r) * 0.5f - offset) / roughness1, 1.0f);
+
+	float theta_h = (theta_i + theta_r) * 0.5f;
+	float t = theta_h - offset;
+
+	float phi_pdf = cos(phi_i * 0.5f) * 0.25f / roughness2;
+	float theta_pdf = roughness1 / (2 * (t*t + roughness1*roughness1) * (a_R - b_R)* costheta_i);
+	*pdf = phi_pdf * theta_pdf;
+
+	return make_float3(*pdf, *pdf, *pdf);
+}
+
+__device float3 bsdf_hair_transmission_eval_reflect(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf)
+{
+	return make_float3(0.0f, 0.0f, 0.0f);
+}
+
+
+__device float3 bsdf_hair_reflection_eval_transmit(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf)
+{
+	return make_float3(0.0f, 0.0f, 0.0f);
+}
+
+__device float3 bsdf_hair_transmission_eval_transmit(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf)
+{
+#ifdef __HAIR__
+	float offset = sc->offset;
+	float3 Tg = sc->T;
+#else
+	float offset = 0.0f;
+	float3 Tg = make_float3(1.0f,0.0f,0.0f);
+#endif
+	float roughness1 = sc->data0;
+	float roughness2 = sc->data1;
+	float Iz = dot(Tg, I);
+	float3 locy = normalize(I - Tg * Iz);
+	float3 locx = cross(locy, Tg);
+
+	float theta_r = M_PI_2_F - safe_acosf(Iz);
+
+	float omega_in_z = dot(Tg, omega_in);
+	float3 omega_in_y = normalize(omega_in - Tg * omega_in_z);
+
+	float theta_i = M_PI_2_F - safe_acosf(omega_in_z);
+	float phi_i = safe_acosf(dot(omega_in_y, locy));
+
+	if(M_PI_2_F - fabsf(theta_i) < 0.001f){
+		*pdf = 0.0f;
+		return make_float3(*pdf, *pdf, *pdf);
+	}
+
+	float costheta_i = cosf(theta_i);
+
+	float a_TT = atan2f(((M_PI_2_F + theta_r)/2 - offset) / roughness1, 1.0f);
+	float b_TT = atan2f(((-M_PI_2_F + theta_r)/2 - offset) / roughness1, 1.0f);
+	float c_TT = 2 * atan2f(M_PI_2_F / roughness2, 1.0f);
+
+	float theta_h = (theta_i + theta_r) / 2;
+	float t = theta_h - offset;
+	float phi = fabsf(phi_i);
+
+	float p = M_PI_F - phi;
+	float theta_pdf = roughness1 / (2 * (t*t + roughness1 * roughness1) * (a_TT - b_TT)*costheta_i);
+	float phi_pdf = roughness2 / (c_TT * (p * p + roughness2 * roughness2));
+
+	*pdf = phi_pdf * theta_pdf;
+	return make_float3(*pdf, *pdf, *pdf);
+}
+
+__device int bsdf_hair_reflection_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)
+{
+#ifdef __HAIR__
+	float offset = sc->offset;
+	float3 Tg = sc->T;
+#else
+	float offset = 0.0f;
+	float3 Tg = make_float3(1.0f,0.0f,0.0f);
+#endif
+	float roughness1 = sc->data0;
+	float roughness2 = sc->data1;
+	float Iz = dot(Tg, I);
+	float3 locy = normalize(I - Tg * Iz);
+	float3 locx = cross(locy, Tg);
+	float theta_r = M_PI_2_F - safe_acosf(Iz);
+
+	float a_R = atan2f(((M_PI_2_F + theta_r) * 0.5f - offset) / roughness1, 1.0f);
+	float b_R = atan2f(((-M_PI_2_F + theta_r) * 0.5f - offset) / roughness1, 1.0f);
+
+	float t = roughness1 * tanf(randu * (a_R - b_R) + b_R);
+
+	float theta_h = t + offset;
+	float theta_i = 2 * theta_h - theta_r;
+	float costheta_i = cosf(theta_i);
+	float sintheta_i = sinf(theta_i);
+
+	float phi = 2 * safe_asinf(1 - 2 * randv) * roughness2;
+
+	float phi_pdf = cos(phi * 0.5f) * 0.25f / roughness2;
+
+	float theta_pdf = roughness1 / (2 * (t*t + roughness1*roughness1) * (a_R - b_R)*costheta_i);
+
+	*omega_in =(cosf(phi) * costheta_i) * locy -
+			   (sinf(phi) * costheta_i) * locx +
+			   (            sintheta_i) * Tg;
+
+	//differentials - TODO: find a better approximation for the reflective bounce
+#ifdef __RAY_DIFFERENTIALS__
+	*domega_in_dx = 2 * dot(locy, dIdx) * locy - dIdx;
+	*domega_in_dy = 2 * dot(locy, dIdy) * locy - dIdy;
+#endif
+
+	*pdf = fabsf(phi_pdf * theta_pdf);
+	if(M_PI_2_F - fabsf(theta_i) < 0.001f)
+		*pdf = 0.0f;
+
+	*eval = make_float3(*pdf, *pdf, *pdf);
+
+	if(dot(locy, *omega_in) < 0.0f) {
+		return LABEL_REFLECT|LABEL_TRANSMIT|LABEL_GLOSSY;
+	}
+	
+	return LABEL_REFLECT|LABEL_GLOSSY;
+}
+
+__device int bsdf_hair_transmission_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)
+{
+#ifdef __HAIR__
+	float offset = sc->offset;
+	float3 Tg = sc->T;
+#else
+	float offset = 0.0f;
+	float3 Tg = make_float3(1.0f,0.0f,0.0f);
+#endif
+	float roughness1 = sc->data0;
+	float roughness2 = sc->data1;
+	float Iz = dot(Tg, I);
+	float3 locy = normalize(I - Tg * Iz);
+	float3 locx = cross(locy, Tg);
+	float theta_r = M_PI_2_F - safe_acosf(Iz);
+
+	float a_TT = atan2f(((M_PI_2_F + theta_r)/2 - offset) / roughness1, 1.0f);
+	float b_TT = atan2f(((-M_PI_2_F + theta_r)/2 - offset) / roughness1, 1.0f);
+	float c_TT = 2 * atan2f(M_PI_2_F / roughness2, 1.0f);
+
+	float t = roughness1 * tanf(randu * (a_TT - b_TT) + b_TT);
+
+	float theta_h = t + offset;
+	float theta_i = 2 * theta_h - theta_r;
+	float costheta_i = cosf(theta_i);
+	float sintheta_i = sinf(theta_i);
+
+	float p = roughness2 * tanf(c_TT * (randv - 0.5f));
+	float phi = p + M_PI_F;
+	float theta_pdf = roughness1 / (2 * (t*t + roughness1*roughness1) * (a_TT - b_TT) * costheta_i);
+	float phi_pdf = roughness2 / (c_TT * (p * p + roughness2 * roughness2));
+
+	*omega_in =(cosf(phi) * costheta_i) * locy -
+			   (sinf(phi) * costheta_i) * locx +
+			   (            sintheta_i) * Tg;
+
+	//differentials - TODO: find a better approximation for the transmission bounce
+#ifdef __RAY_DIFFERENTIALS__
+	*domega_in_dx = 2 * dot(locy, dIdx) * locy - dIdx;
+	*domega_in_dy = 2 * dot(locy, dIdy) * locy - dIdy;
+#endif
+
+	*pdf = fabsf(phi_pdf * theta_pdf);
+	if(M_PI_2_F - fabsf(theta_i) < 0.001f){
+		*pdf = 0.0f;
+	}
+
+	*eval = make_float3(*pdf, *pdf, *pdf);
+
+	if(dot(locy, *omega_in) < 0.0f)
+		return LABEL_TRANSMIT|LABEL_GLOSSY;
+	
+	return LABEL_GLOSSY;
+}
+
+CCL_NAMESPACE_END
+
+#endif /* __BSDF_HAIR_H__ */
+