forked from bartvdbraak/blender
Brecht Van Lommel
a3abb020e3
Mostly this is making inlining match CUDA 7.5 in a few performance critical places. The end result is that performance is now better than before, possibly due to less register spilling or other CUDA 8.0 compiler improvements. On benchmarks scenes, there are 3% to 35% render time reductions. Stack memory usage is reduced a little too. Reviewed By: sergey Differential Revision: https://developer.blender.org/D2269
234 lines
7.7 KiB
C
234 lines
7.7 KiB
C
/*
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* Copyright 2011-2016 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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/* Evaluate the BSDF from wi to wo.
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* Evaluation is split into the analytical single-scattering BSDF and the multi-scattering BSDF,
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* which is evaluated stochastically through a random walk. At each bounce (except for the first one),
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* the amount of reflection from here towards wo is evaluated before bouncing again.
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*
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* Because of the random walk, the evaluation is not deterministic, but its expected value is equal to
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* the correct BSDF, which is enough for Monte-Carlo rendering. The PDF also can't be determined
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* analytically, so the single-scattering PDF plus a diffuse term to account for the multi-scattered
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* energy is used. In combination with MIS, that is enough to produce an unbiased result, although
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* the balance heuristic isn't necessarily optimal anymore.
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*/
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ccl_device_forceinline float3 MF_FUNCTION_FULL_NAME(mf_eval)(
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float3 wi,
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float3 wo,
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const bool wo_outside,
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const float3 color,
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const float alpha_x,
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const float alpha_y,
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ccl_addr_space uint *lcg_state
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#ifdef MF_MULTI_GLASS
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, const float eta
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#elif defined(MF_MULTI_GLOSSY)
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, float3 *n, float3 *k
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#endif
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)
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{
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/* Evaluating for a shallower incoming direction produces less noise, and the properties of the BSDF guarantee reciprocity. */
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bool swapped = false;
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#ifdef MF_MULTI_GLASS
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if(wi.z*wo.z < 0.0f) {
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/* Glass transmission is a special case and requires the directions to change hemisphere. */
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if(-wo.z < wi.z) {
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swapped = true;
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float3 tmp = -wo;
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wo = -wi;
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wi = tmp;
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}
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}
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else
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#endif
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if(wo.z < wi.z) {
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swapped = true;
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float3 tmp = wo;
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wo = wi;
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wi = tmp;
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}
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if(wi.z < 1e-5f || (wo.z < 1e-5f && wo_outside) || (wo.z > -1e-5f && !wo_outside))
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return make_float3(0.0f, 0.0f, 0.0f);
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const float2 alpha = make_float2(alpha_x, alpha_y);
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float lambda_r = mf_lambda(-wi, alpha);
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float shadowing_lambda = mf_lambda(wo_outside? wo: -wo, alpha);
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/* Analytically compute single scattering for lower noise. */
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float3 eval;
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#ifdef MF_MULTI_GLASS
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eval = mf_eval_phase_glass(-wi, lambda_r, wo, wo_outside, alpha, eta);
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if(wo_outside)
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eval *= -lambda_r / (shadowing_lambda - lambda_r);
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else
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eval *= -lambda_r * beta(-lambda_r, shadowing_lambda+1.0f);
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#elif defined(MF_MULTI_DIFFUSE)
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/* Diffuse has no special closed form for the single scattering bounce */
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eval = make_float3(0.0f, 0.0f, 0.0f);
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#else /* MF_MULTI_GLOSSY */
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const float3 wh = normalize(wi+wo);
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const float G2 = 1.0f / (1.0f - (lambda_r + 1.0f) + shadowing_lambda);
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float val = G2 * 0.25f / wi.z;
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if(alpha.x == alpha.y)
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val *= D_ggx(wh, alpha.x);
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else
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val *= D_ggx_aniso(wh, alpha);
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if(n && k) {
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eval = fresnel_conductor(dot(wh, wi), *n, *k) * val;
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}
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else {
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eval = make_float3(val, val, val);
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}
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#endif
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float3 wr = -wi;
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float hr = 1.0f;
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float C1_r = 1.0f;
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float G1_r = 0.0f;
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bool outside = true;
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float3 throughput = make_float3(1.0f, 1.0f, 1.0f);
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for(int order = 0; order < 10; order++) {
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/* Sample microfacet height and normal */
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if(!mf_sample_height(wr, &hr, &C1_r, &G1_r, &lambda_r, lcg_step_float_addrspace(lcg_state)))
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break;
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float3 wm = mf_sample_vndf(-wr, alpha, make_float2(lcg_step_float_addrspace(lcg_state),
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lcg_step_float_addrspace(lcg_state)));
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#ifdef MF_MULTI_DIFFUSE
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if(order == 0) {
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/* Compute single-scattering for diffuse. */
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const float G2_G1 = -lambda_r / (shadowing_lambda - lambda_r);
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eval += throughput * G2_G1 * mf_eval_phase_diffuse(wo, wm);
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}
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#endif
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if(order > 0) {
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/* Evaluate amount of scattering towards wo on this microfacet. */
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float3 phase;
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#ifdef MF_MULTI_GLASS
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if(outside)
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phase = mf_eval_phase_glass(wr, lambda_r, wo, wo_outside, alpha, eta);
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else
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phase = mf_eval_phase_glass(wr, lambda_r, -wo, !wo_outside, alpha, 1.0f/eta);
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#elif defined(MF_MULTI_DIFFUSE)
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phase = mf_eval_phase_diffuse(wo, wm);
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#else /* MF_MULTI_GLOSSY */
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phase = mf_eval_phase_glossy(wr, lambda_r, wo, alpha, n, k) * throughput;
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#endif
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eval += throughput * phase * mf_G1(wo_outside? wo: -wo, mf_C1((outside == wo_outside)? hr: -hr), shadowing_lambda);
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}
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if(order+1 < 10) {
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/* Bounce from the microfacet. */
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#ifdef MF_MULTI_GLASS
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bool next_outside;
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wr = mf_sample_phase_glass(-wr, outside? eta: 1.0f/eta, wm, lcg_step_float_addrspace(lcg_state), &next_outside);
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if(!next_outside) {
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outside = !outside;
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wr = -wr;
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hr = -hr;
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}
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#elif defined(MF_MULTI_DIFFUSE)
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wr = mf_sample_phase_diffuse(wm,
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lcg_step_float_addrspace(lcg_state),
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lcg_step_float_addrspace(lcg_state));
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#else /* MF_MULTI_GLOSSY */
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wr = mf_sample_phase_glossy(-wr, n, k, &throughput, wm);
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#endif
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lambda_r = mf_lambda(wr, alpha);
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throughput *= color;
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C1_r = mf_C1(hr);
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G1_r = mf_G1(wr, C1_r, lambda_r);
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}
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}
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if(swapped)
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eval *= fabsf(wi.z / wo.z);
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return eval;
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}
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/* Perform a random walk on the microsurface starting from wi, returning the direction in which the walk
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* escaped the surface in wo. The function returns the throughput between wi and wo.
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* Without reflection losses due to coloring or fresnel absorption in conductors, the sampling is optimal.
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*/
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ccl_device_forceinline float3 MF_FUNCTION_FULL_NAME(mf_sample)(float3 wi, float3 *wo, const float3 color, const float alpha_x, const float alpha_y, ccl_addr_space uint *lcg_state
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#ifdef MF_MULTI_GLASS
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, const float eta
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#elif defined(MF_MULTI_GLOSSY)
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, float3 *n, float3 *k
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#endif
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)
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{
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const float2 alpha = make_float2(alpha_x, alpha_y);
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float3 throughput = make_float3(1.0f, 1.0f, 1.0f);
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float3 wr = -wi;
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float lambda_r = mf_lambda(wr, alpha);
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float hr = 1.0f;
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float C1_r = 1.0f;
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float G1_r = 0.0f;
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bool outside = true;
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int order;
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for(order = 0; order < 10; order++) {
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/* Sample microfacet height. */
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if(!mf_sample_height(wr, &hr, &C1_r, &G1_r, &lambda_r, lcg_step_float_addrspace(lcg_state))) {
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/* The random walk has left the surface. */
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*wo = outside? wr: -wr;
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return throughput;
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}
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/* Sample microfacet normal. */
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float3 wm = mf_sample_vndf(-wr, alpha, make_float2(lcg_step_float_addrspace(lcg_state),
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lcg_step_float_addrspace(lcg_state)));
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/* First-bounce color is already accounted for in mix weight. */
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if(order > 0)
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throughput *= color;
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/* Bounce from the microfacet. */
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#ifdef MF_MULTI_GLASS
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bool next_outside;
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wr = mf_sample_phase_glass(-wr, outside? eta: 1.0f/eta, wm, lcg_step_float_addrspace(lcg_state), &next_outside);
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if(!next_outside) {
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hr = -hr;
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wr = -wr;
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outside = !outside;
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}
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#elif defined(MF_MULTI_DIFFUSE)
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wr = mf_sample_phase_diffuse(wm,
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lcg_step_float_addrspace(lcg_state),
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lcg_step_float_addrspace(lcg_state));
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#else /* MF_MULTI_GLOSSY */
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wr = mf_sample_phase_glossy(-wr, n, k, &throughput, wm);
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#endif
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/* Update random walk parameters. */
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lambda_r = mf_lambda(wr, alpha);
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G1_r = mf_G1(wr, C1_r, lambda_r);
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}
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*wo = make_float3(0.0f, 0.0f, 1.0f);
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return make_float3(0.0f, 0.0f, 0.0f);
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}
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#undef MF_MULTI_GLASS
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#undef MF_MULTI_DIFFUSE
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#undef MF_MULTI_GLOSSY
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#undef MF_PHASE_FUNCTION
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