253 lines
8.4 KiB
C
253 lines
8.4 KiB
C
/* SPDX-FileCopyrightText: 2009-2010 Sony Pictures Imageworks Inc., et al. All Rights Reserved.
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* SPDX-FileCopyrightText: 2011-2022 Blender Foundation
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*
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* Adapted code from Open Shading Language. */
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#pragma once
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CCL_NAMESPACE_BEGIN
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typedef struct HairBsdf {
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SHADER_CLOSURE_BASE;
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float3 T;
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float roughness1;
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float roughness2;
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float offset;
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} HairBsdf;
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static_assert(sizeof(ShaderClosure) >= sizeof(HairBsdf), "HairBsdf is too large!");
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ccl_device int bsdf_hair_reflection_setup(ccl_private HairBsdf *bsdf)
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{
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bsdf->type = CLOSURE_BSDF_HAIR_REFLECTION_ID;
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bsdf->roughness1 = clamp(bsdf->roughness1, 0.001f, 1.0f);
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bsdf->roughness2 = clamp(bsdf->roughness2, 0.001f, 1.0f);
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return SD_BSDF | SD_BSDF_HAS_EVAL;
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}
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ccl_device int bsdf_hair_transmission_setup(ccl_private HairBsdf *bsdf)
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{
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bsdf->type = CLOSURE_BSDF_HAIR_TRANSMISSION_ID;
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bsdf->roughness1 = clamp(bsdf->roughness1, 0.001f, 1.0f);
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bsdf->roughness2 = clamp(bsdf->roughness2, 0.001f, 1.0f);
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return SD_BSDF | SD_BSDF_HAS_EVAL | SD_BSDF_HAS_TRANSMISSION;
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}
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ccl_device Spectrum bsdf_hair_reflection_eval(ccl_private const ShaderClosure *sc,
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const float3 wi,
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const float3 wo,
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ccl_private float *pdf)
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{
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ccl_private const HairBsdf *bsdf = (ccl_private const HairBsdf *)sc;
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if (dot(bsdf->N, wo) < 0.0f) {
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*pdf = 0.0f;
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return zero_spectrum();
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}
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float offset = bsdf->offset;
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float3 Tg = bsdf->T;
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float roughness1 = bsdf->roughness1;
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float roughness2 = bsdf->roughness2;
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float Iz = dot(Tg, wi);
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float3 locy = normalize(wi - Tg * Iz);
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float theta_r = M_PI_2_F - fast_acosf(Iz);
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float wo_z = dot(Tg, wo);
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float3 wo_y = normalize(wo - Tg * wo_z);
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float theta_i = M_PI_2_F - fast_acosf(wo_z);
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float cosphi_i = dot(wo_y, locy);
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if (M_PI_2_F - fabsf(theta_i) < 0.001f || cosphi_i < 0.0f) {
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*pdf = 0.0f;
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return zero_spectrum();
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}
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float roughness1_inv = 1.0f / roughness1;
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float roughness2_inv = 1.0f / roughness2;
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float phi_i = fast_acosf(cosphi_i) * roughness2_inv;
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phi_i = fabsf(phi_i) < M_PI_F ? phi_i : M_PI_F;
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float costheta_i = fast_cosf(theta_i);
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float a_R = fast_atan2f(((M_PI_2_F + theta_r) * 0.5f - offset) * roughness1_inv, 1.0f);
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float b_R = fast_atan2f(((-M_PI_2_F + theta_r) * 0.5f - offset) * roughness1_inv, 1.0f);
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float theta_h = (theta_i + theta_r) * 0.5f;
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float t = theta_h - offset;
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float phi_pdf = fast_cosf(phi_i * 0.5f) * 0.25f * roughness2_inv;
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float theta_pdf = roughness1 /
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(2 * (t * t + roughness1 * roughness1) * (a_R - b_R) * costheta_i);
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*pdf = phi_pdf * theta_pdf;
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return make_spectrum(*pdf);
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}
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ccl_device Spectrum bsdf_hair_transmission_eval(ccl_private const ShaderClosure *sc,
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const float3 wi,
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const float3 wo,
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ccl_private float *pdf)
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{
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ccl_private const HairBsdf *bsdf = (ccl_private const HairBsdf *)sc;
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if (dot(bsdf->N, wo) >= 0.0f) {
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*pdf = 0.0f;
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return zero_spectrum();
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}
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float offset = bsdf->offset;
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float3 Tg = bsdf->T;
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float roughness1 = bsdf->roughness1;
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float roughness2 = bsdf->roughness2;
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float Iz = dot(Tg, wi);
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float3 locy = normalize(wi - Tg * Iz);
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float theta_r = M_PI_2_F - fast_acosf(Iz);
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float wo_z = dot(Tg, wo);
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float3 wo_y = normalize(wo - Tg * wo_z);
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float theta_i = M_PI_2_F - fast_acosf(wo_z);
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float phi_i = fast_acosf(dot(wo_y, locy));
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if (M_PI_2_F - fabsf(theta_i) < 0.001f) {
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*pdf = 0.0f;
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return zero_spectrum();
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}
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float costheta_i = fast_cosf(theta_i);
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float roughness1_inv = 1.0f / roughness1;
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float a_TT = fast_atan2f(((M_PI_2_F + theta_r) / 2 - offset) * roughness1_inv, 1.0f);
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float b_TT = fast_atan2f(((-M_PI_2_F + theta_r) / 2 - offset) * roughness1_inv, 1.0f);
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float c_TT = 2 * fast_atan2f(M_PI_2_F / roughness2, 1.0f);
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float theta_h = (theta_i + theta_r) / 2;
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float t = theta_h - offset;
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float phi = fabsf(phi_i);
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float p = M_PI_F - phi;
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float theta_pdf = roughness1 /
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(2 * (t * t + roughness1 * roughness1) * (a_TT - b_TT) * costheta_i);
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float phi_pdf = roughness2 / (c_TT * (p * p + roughness2 * roughness2));
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*pdf = phi_pdf * theta_pdf;
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return make_spectrum(*pdf);
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}
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ccl_device int bsdf_hair_reflection_sample(ccl_private const ShaderClosure *sc,
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float3 Ng,
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float3 wi,
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float2 rand,
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ccl_private Spectrum *eval,
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ccl_private float3 *wo,
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ccl_private float *pdf,
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ccl_private float2 *sampled_roughness)
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{
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ccl_private const HairBsdf *bsdf = (ccl_private const HairBsdf *)sc;
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float offset = bsdf->offset;
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float3 Tg = bsdf->T;
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float roughness1 = bsdf->roughness1;
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float roughness2 = bsdf->roughness2;
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*sampled_roughness = make_float2(roughness1, roughness2);
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float Iz = dot(Tg, wi);
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float3 locy = normalize(wi - Tg * Iz);
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float3 locx = cross(locy, Tg);
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float theta_r = M_PI_2_F - fast_acosf(Iz);
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float roughness1_inv = 1.0f / roughness1;
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float a_R = fast_atan2f(((M_PI_2_F + theta_r) * 0.5f - offset) * roughness1_inv, 1.0f);
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float b_R = fast_atan2f(((-M_PI_2_F + theta_r) * 0.5f - offset) * roughness1_inv, 1.0f);
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float t = roughness1 * tanf(rand.x * (a_R - b_R) + b_R);
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float theta_h = t + offset;
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float theta_i = 2 * theta_h - theta_r;
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float costheta_i, sintheta_i;
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fast_sincosf(theta_i, &sintheta_i, &costheta_i);
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float phi = 2 * safe_asinf(1 - 2 * rand.y) * roughness2;
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float phi_pdf = fast_cosf(phi * 0.5f) * 0.25f / roughness2;
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float theta_pdf = roughness1 /
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(2 * (t * t + roughness1 * roughness1) * (a_R - b_R) * costheta_i);
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float sinphi, cosphi;
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fast_sincosf(phi, &sinphi, &cosphi);
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*wo = (cosphi * costheta_i) * locy - (sinphi * costheta_i) * locx + (sintheta_i)*Tg;
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*pdf = fabsf(phi_pdf * theta_pdf);
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if (M_PI_2_F - fabsf(theta_i) < 0.001f)
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*pdf = 0.0f;
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*eval = make_spectrum(*pdf);
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return LABEL_REFLECT | LABEL_GLOSSY;
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}
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ccl_device int bsdf_hair_transmission_sample(ccl_private const ShaderClosure *sc,
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float3 Ng,
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float3 wi,
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float2 rand,
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ccl_private Spectrum *eval,
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ccl_private float3 *wo,
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ccl_private float *pdf,
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ccl_private float2 *sampled_roughness)
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{
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ccl_private const HairBsdf *bsdf = (ccl_private const HairBsdf *)sc;
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float offset = bsdf->offset;
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float3 Tg = bsdf->T;
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float roughness1 = bsdf->roughness1;
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float roughness2 = bsdf->roughness2;
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*sampled_roughness = make_float2(roughness1, roughness2);
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float Iz = dot(Tg, wi);
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float3 locy = normalize(wi - Tg * Iz);
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float3 locx = cross(locy, Tg);
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float theta_r = M_PI_2_F - fast_acosf(Iz);
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float roughness1_inv = 1.0f / roughness1;
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float a_TT = fast_atan2f(((M_PI_2_F + theta_r) / 2 - offset) * roughness1_inv, 1.0f);
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float b_TT = fast_atan2f(((-M_PI_2_F + theta_r) / 2 - offset) * roughness1_inv, 1.0f);
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float c_TT = 2 * fast_atan2f(M_PI_2_F / roughness2, 1.0f);
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float t = roughness1 * tanf(rand.x * (a_TT - b_TT) + b_TT);
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float theta_h = t + offset;
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float theta_i = 2 * theta_h - theta_r;
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float costheta_i, sintheta_i;
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fast_sincosf(theta_i, &sintheta_i, &costheta_i);
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float p = roughness2 * tanf(c_TT * (rand.y - 0.5f));
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float phi = p + M_PI_F;
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float theta_pdf = roughness1 /
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(2 * (t * t + roughness1 * roughness1) * (a_TT - b_TT) * costheta_i);
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float phi_pdf = roughness2 / (c_TT * (p * p + roughness2 * roughness2));
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float sinphi, cosphi;
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fast_sincosf(phi, &sinphi, &cosphi);
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*wo = (cosphi * costheta_i) * locy - (sinphi * costheta_i) * locx + (sintheta_i)*Tg;
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*pdf = fabsf(phi_pdf * theta_pdf);
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if (M_PI_2_F - fabsf(theta_i) < 0.001f) {
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*pdf = 0.0f;
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}
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*eval = make_spectrum(*pdf);
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/* TODO(sergey): Should always be negative, but seems some precision issue
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* is involved here.
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*/
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kernel_assert(dot(locy, *wo) < 1e-4f);
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return LABEL_TRANSMIT | LABEL_GLOSSY;
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}
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CCL_NAMESPACE_END
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