543bf28fb1
wi is the viewing direction, and wo is the illumination direction. Under this notation, BSDF sampling always samples from wi and outputs wo, which is consistent with most of the papers and mitsuba. This order is reversed compared with PBRT, although PBRT also traces from the camera.
127 lines
4.0 KiB
C
127 lines
4.0 KiB
C
/* SPDX-License-Identifier: BSD-3-Clause
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*
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* Adapted from Open Shading Language
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* Copyright (c) 2009-2010 Sony Pictures Imageworks Inc., et al.
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* All Rights Reserved.
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*
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* Modifications Copyright 2011-2022 Blender Foundation. */
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#pragma once
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#include "kernel/util/color.h"
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CCL_NAMESPACE_BEGIN
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#ifdef __OSL__
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typedef struct PhongRampBsdf {
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SHADER_CLOSURE_BASE;
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float exponent;
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ccl_private float3 *colors;
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} PhongRampBsdf;
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static_assert(sizeof(ShaderClosure) >= sizeof(PhongRampBsdf), "PhongRampBsdf is too large!");
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ccl_device float3 bsdf_phong_ramp_get_color(const float3 colors[8], float pos)
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{
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int MAXCOLORS = 8;
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float npos = pos * (float)(MAXCOLORS - 1);
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int ipos = float_to_int(npos);
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if (ipos < 0)
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return colors[0];
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if (ipos >= (MAXCOLORS - 1))
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return colors[MAXCOLORS - 1];
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float offset = npos - (float)ipos;
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return colors[ipos] * (1.0f - offset) + colors[ipos + 1] * offset;
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}
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ccl_device int bsdf_phong_ramp_setup(ccl_private PhongRampBsdf *bsdf)
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{
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bsdf->type = CLOSURE_BSDF_PHONG_RAMP_ID;
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bsdf->exponent = max(bsdf->exponent, 0.0f);
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return SD_BSDF | SD_BSDF_HAS_EVAL;
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}
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ccl_device Spectrum bsdf_phong_ramp_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 PhongRampBsdf *bsdf = (ccl_private const PhongRampBsdf *)sc;
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float m_exponent = bsdf->exponent;
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float cosNI = dot(bsdf->N, wi);
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float cosNO = dot(bsdf->N, wo);
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if (cosNI > 0 && cosNO > 0) {
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// reflect the view vector
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float3 R = (2 * cosNI) * bsdf->N - wi;
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float cosRO = dot(R, wo);
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if (cosRO > 0) {
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float cosp = powf(cosRO, m_exponent);
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float common = 0.5f * M_1_PI_F * cosp;
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float out = cosNO * (m_exponent + 2) * common;
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*pdf = (m_exponent + 1) * common;
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return rgb_to_spectrum(bsdf_phong_ramp_get_color(bsdf->colors, cosp) * out);
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}
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}
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*pdf = 0.0f;
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return zero_spectrum();
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}
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ccl_device_inline float phong_ramp_exponent_to_roughness(float exponent)
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{
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return sqrt(1.0f / ((exponent + 2.0f) / 2.0f));
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}
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ccl_device int bsdf_phong_ramp_sample(ccl_private const ShaderClosure *sc,
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float3 Ng,
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float3 wi,
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float randu,
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float randv,
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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 PhongRampBsdf *bsdf = (ccl_private const PhongRampBsdf *)sc;
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float cosNI = dot(bsdf->N, wi);
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float m_exponent = bsdf->exponent;
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const float m_roughness = phong_ramp_exponent_to_roughness(m_exponent);
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*sampled_roughness = make_float2(m_roughness, m_roughness);
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if (cosNI > 0) {
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// reflect the view vector
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float3 R = (2 * cosNI) * bsdf->N - wi;
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float3 T, B;
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make_orthonormals(R, &T, &B);
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float phi = M_2PI_F * randu;
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float cosTheta = powf(randv, 1 / (m_exponent + 1));
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float sinTheta2 = 1 - cosTheta * cosTheta;
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float sinTheta = sinTheta2 > 0 ? sqrtf(sinTheta2) : 0;
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*wo = (cosf(phi) * sinTheta) * T + (sinf(phi) * sinTheta) * B + (cosTheta)*R;
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if (dot(Ng, *wo) > 0.0f) {
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// common terms for pdf and eval
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float cosNO = dot(bsdf->N, *wo);
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// make sure the direction we chose is still in the right hemisphere
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if (cosNO > 0) {
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float cosp = powf(cosTheta, m_exponent);
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float common = 0.5f * M_1_PI_F * cosp;
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*pdf = (m_exponent + 1) * common;
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float out = cosNO * (m_exponent + 2) * common;
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*eval = rgb_to_spectrum(bsdf_phong_ramp_get_color(bsdf->colors, cosp) * out);
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}
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}
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}
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else {
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*eval = zero_spectrum();
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*pdf = 0.0f;
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}
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return LABEL_REFLECT | LABEL_GLOSSY;
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}
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#endif /* __OSL__ */
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CCL_NAMESPACE_END
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