forked from bartvdbraak/blender
143 lines
4.0 KiB
C
143 lines
4.0 KiB
C
/*
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* Copyright 2011-2013 Blender Foundation
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef __VOLUME_H__
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#define __VOLUME_H__
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CCL_NAMESPACE_BEGIN
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/* HENYEY-GREENSTEIN CLOSURE */
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/* Given cosine between rays, return probability density that a photon bounces
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* to that direction. The g parameter controls how different it is from the
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* uniform sphere. g=0 uniform diffuse-like, g=1 close to sharp single ray. */
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ccl_device float single_peaked_henyey_greenstein(float cos_theta, float g)
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{
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if(fabsf(g) < 1e-3f)
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return M_1_PI_F * 0.25f;
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return ((1.0f - g * g) / safe_powf(1.0f + g * g - 2.0f * g * cos_theta, 1.5f)) * (M_1_PI_F * 0.25f);
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};
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ccl_device int volume_henyey_greenstein_setup(ShaderClosure *sc)
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{
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sc->type = CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID;
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/* clamp anisotropy to avoid delta function */
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sc->data0 = signf(sc->data0) * min(fabsf(sc->data0), 1.0f - 1e-3f);
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return SD_SCATTER|SD_PHASE_HAS_EVAL;
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}
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ccl_device float3 volume_henyey_greenstein_eval_phase(const ShaderClosure *sc, const float3 I, float3 omega_in, float *pdf)
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{
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float g = sc->data0;
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/* note that I points towards the viewer */
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float cos_theta = dot(-I, omega_in);
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*pdf = single_peaked_henyey_greenstein(cos_theta, g);
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return make_float3(*pdf, *pdf, *pdf);
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}
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ccl_device int volume_henyey_greenstein_sample(const ShaderClosure *sc, float3 I, float3 dIdx, float3 dIdy, float randu, float randv,
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float3 *eval, float3 *omega_in, float3 *domega_in_dx, float3 *domega_in_dy, float *pdf)
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{
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float g = sc->data0;
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float cos_phi, sin_phi, cos_theta;
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/* match pdf for small g */
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if(fabsf(g) < 1e-3f) {
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cos_theta = (1.0f - 2.0f * randu);
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}
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else {
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float k = (1.0f - g * g) / (1.0f - g + 2.0f * g * randu);
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cos_theta = (1.0f + g * g - k * k) / (2.0f * g);
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}
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float sin_theta = safe_sqrtf(1.0f - cos_theta * cos_theta);
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float phi = M_2PI_F * randv;
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cos_phi = cosf(phi);
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sin_phi = sinf(phi);
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/* note that I points towards the viewer and so is used negated */
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float3 T, B;
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make_orthonormals(-I, &T, &B);
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*omega_in = sin_theta * cos_phi * T + sin_theta * sin_phi * B + cos_theta * (-I);
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*pdf = single_peaked_henyey_greenstein(cos_theta, g);
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*eval = make_float3(*pdf, *pdf, *pdf); /* perfect importance sampling */
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#ifdef __RAY_DIFFERENTIALS__
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/* todo: implement ray differential estimation */
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*domega_in_dx = make_float3(0.0f, 0.0f, 0.0f);
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*domega_in_dy = make_float3(0.0f, 0.0f, 0.0f);
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#endif
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return LABEL_VOLUME_SCATTER;
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}
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/* ABSORPTION VOLUME CLOSURE */
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ccl_device int volume_absorption_setup(ShaderClosure *sc)
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{
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sc->type = CLOSURE_VOLUME_ABSORPTION_ID;
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return SD_ABSORPTION;
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}
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/* VOLUME CLOSURE */
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ccl_device float3 volume_phase_eval(const ShaderData *sd, const ShaderClosure *sc, float3 omega_in, float *pdf)
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{
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float3 eval;
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switch(sc->type) {
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case CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID:
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eval = volume_henyey_greenstein_eval_phase(sc, sd->I, omega_in, pdf);
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break;
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default:
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eval = make_float3(0.0f, 0.0f, 0.0f);
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break;
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}
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return eval;
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}
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ccl_device int volume_phase_sample(const ShaderData *sd, const ShaderClosure *sc, float randu,
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float randv, float3 *eval, float3 *omega_in, differential3 *domega_in, float *pdf)
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{
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int label;
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switch(sc->type) {
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case CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID:
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label = volume_henyey_greenstein_sample(sc, sd->I, sd->dI.dx, sd->dI.dy, randu, randv, eval, omega_in, &domega_in->dx, &domega_in->dy, pdf);
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break;
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default:
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*eval = make_float3(0.0f, 0.0f, 0.0f);
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label = LABEL_NONE;
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break;
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}
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return label;
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}
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CCL_NAMESPACE_END
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#endif
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