forked from bartvdbraak/blender
07de832e22
The light sampling functions calculate light sampling PDF for the case that the light has been randomly selected out of all lights. However, since BPT handles lamps and meshlights separately, this isn't the case. So, to avoid a wrong result, the code just included the 0.5 factor in the throughput. In theory, however, the correction should be made to the sampling probability, which needs to be doubled. Now, for the regular calculation, that's no real difference since the throughput is divided by the pdf. However, it does matter for the MIS calculation - it's unbiased both ways, but including the factor in the PDF instead of the throughput should give slightly better results. Reviewers: sergey, brecht, dingto, juicyfruit Differential Revision: https://developer.blender.org/D2258
320 lines
10 KiB
C
320 lines
10 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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CCL_NAMESPACE_BEGIN
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#if defined(__BRANCHED_PATH__) || defined(__SUBSURFACE__)
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/* branched path tracing: connect path directly to position on one or more lights and add it to L */
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ccl_device_noinline void kernel_branched_path_surface_connect_light(KernelGlobals *kg, RNG *rng,
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ShaderData *sd, ShaderData *emission_sd, PathState *state, float3 throughput,
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float num_samples_adjust, PathRadiance *L, int sample_all_lights)
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{
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#ifdef __EMISSION__
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/* sample illumination from lights to find path contribution */
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if(!(ccl_fetch(sd, flag) & SD_BSDF_HAS_EVAL))
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return;
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Ray light_ray;
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BsdfEval L_light;
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bool is_lamp;
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# ifdef __OBJECT_MOTION__
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light_ray.time = ccl_fetch(sd, time);
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# endif
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if(sample_all_lights) {
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/* lamp sampling */
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for(int i = 0; i < kernel_data.integrator.num_all_lights; i++) {
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if(UNLIKELY(light_select_reached_max_bounces(kg, i, state->bounce)))
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continue;
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int num_samples = ceil_to_int(num_samples_adjust*light_select_num_samples(kg, i));
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float num_samples_inv = num_samples_adjust/(num_samples*kernel_data.integrator.num_all_lights);
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RNG lamp_rng = cmj_hash(*rng, i);
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for(int j = 0; j < num_samples; j++) {
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float light_u, light_v;
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path_branched_rng_2D(kg, &lamp_rng, state, j, num_samples, PRNG_LIGHT_U, &light_u, &light_v);
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LightSample ls;
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if(lamp_light_sample(kg, i, light_u, light_v, ccl_fetch(sd, P), &ls)) {
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/* The sampling probability returned by lamp_light_sample assumes that all lights were sampled.
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* However, this code only samples lamps, so if the scene also had mesh lights, the real probability is twice as high. */
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if(kernel_data.integrator.pdf_triangles != 0.0f)
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ls.pdf *= 2.0f;
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if(direct_emission(kg, sd, emission_sd, &ls, state, &light_ray, &L_light, &is_lamp)) {
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/* trace shadow ray */
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float3 shadow;
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if(!shadow_blocked(kg, emission_sd, state, &light_ray, &shadow)) {
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/* accumulate */
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path_radiance_accum_light(L, throughput*num_samples_inv, &L_light, shadow, num_samples_inv, state->bounce, is_lamp);
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}
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}
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}
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}
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}
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/* mesh light sampling */
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if(kernel_data.integrator.pdf_triangles != 0.0f) {
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int num_samples = ceil_to_int(num_samples_adjust*kernel_data.integrator.mesh_light_samples);
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float num_samples_inv = num_samples_adjust/num_samples;
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for(int j = 0; j < num_samples; j++) {
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float light_t = path_branched_rng_1D(kg, rng, state, j, num_samples, PRNG_LIGHT);
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float light_u, light_v;
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path_branched_rng_2D(kg, rng, state, j, num_samples, PRNG_LIGHT_U, &light_u, &light_v);
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/* only sample triangle lights */
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if(kernel_data.integrator.num_all_lights)
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light_t = 0.5f*light_t;
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LightSample ls;
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if(light_sample(kg, light_t, light_u, light_v, ccl_fetch(sd, time), ccl_fetch(sd, P), state->bounce, &ls)) {
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/* Same as above, probability needs to be corrected since the sampling was forced to select a mesh light. */
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if(kernel_data.integrator.num_all_lights)
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ls.pdf *= 2.0f;
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if(direct_emission(kg, sd, emission_sd, &ls, state, &light_ray, &L_light, &is_lamp)) {
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/* trace shadow ray */
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float3 shadow;
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if(!shadow_blocked(kg, emission_sd, state, &light_ray, &shadow)) {
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/* accumulate */
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path_radiance_accum_light(L, throughput*num_samples_inv, &L_light, shadow, num_samples_inv, state->bounce, is_lamp);
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}
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}
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}
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}
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}
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}
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else {
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/* sample one light at random */
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float light_t = path_state_rng_1D(kg, rng, state, PRNG_LIGHT);
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float light_u, light_v;
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path_state_rng_2D(kg, rng, state, PRNG_LIGHT_U, &light_u, &light_v);
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LightSample ls;
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if(light_sample(kg, light_t, light_u, light_v, ccl_fetch(sd, time), ccl_fetch(sd, P), state->bounce, &ls)) {
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/* sample random light */
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if(direct_emission(kg, sd, emission_sd, &ls, state, &light_ray, &L_light, &is_lamp)) {
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/* trace shadow ray */
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float3 shadow;
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if(!shadow_blocked(kg, emission_sd, state, &light_ray, &shadow)) {
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/* accumulate */
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path_radiance_accum_light(L, throughput*num_samples_adjust, &L_light, shadow, num_samples_adjust, state->bounce, is_lamp);
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}
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}
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}
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}
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#endif
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}
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/* branched path tracing: bounce off or through surface to with new direction stored in ray */
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ccl_device bool kernel_branched_path_surface_bounce(KernelGlobals *kg, RNG *rng,
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ShaderData *sd, const ShaderClosure *sc, int sample, int num_samples,
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float3 *throughput, PathState *state, PathRadiance *L, Ray *ray)
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{
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/* sample BSDF */
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float bsdf_pdf;
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BsdfEval bsdf_eval;
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float3 bsdf_omega_in;
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differential3 bsdf_domega_in;
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float bsdf_u, bsdf_v;
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path_branched_rng_2D(kg, rng, state, sample, num_samples, PRNG_BSDF_U, &bsdf_u, &bsdf_v);
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int label;
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label = shader_bsdf_sample_closure(kg, sd, sc, bsdf_u, bsdf_v, &bsdf_eval,
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&bsdf_omega_in, &bsdf_domega_in, &bsdf_pdf);
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if(bsdf_pdf == 0.0f || bsdf_eval_is_zero(&bsdf_eval))
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return false;
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/* modify throughput */
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path_radiance_bsdf_bounce(L, throughput, &bsdf_eval, bsdf_pdf, state->bounce, label);
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/* modify path state */
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path_state_next(kg, state, label);
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/* setup ray */
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ray->P = ray_offset(ccl_fetch(sd, P), (label & LABEL_TRANSMIT)? -ccl_fetch(sd, Ng): ccl_fetch(sd, Ng));
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ray->D = normalize(bsdf_omega_in);
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ray->t = FLT_MAX;
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#ifdef __RAY_DIFFERENTIALS__
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ray->dP = ccl_fetch(sd, dP);
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ray->dD = bsdf_domega_in;
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#endif
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#ifdef __OBJECT_MOTION__
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ray->time = ccl_fetch(sd, time);
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#endif
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#ifdef __VOLUME__
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/* enter/exit volume */
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if(label & LABEL_TRANSMIT)
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kernel_volume_stack_enter_exit(kg, sd, state->volume_stack);
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#endif
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/* branch RNG state */
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path_state_branch(state, sample, num_samples);
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/* set MIS state */
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state->min_ray_pdf = fminf(bsdf_pdf, FLT_MAX);
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state->ray_pdf = bsdf_pdf;
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#ifdef __LAMP_MIS__
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state->ray_t = 0.0f;
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#endif
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return true;
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}
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#endif
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#ifndef __SPLIT_KERNEL__
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/* path tracing: connect path directly to position on a light and add it to L */
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ccl_device_inline void kernel_path_surface_connect_light(KernelGlobals *kg, ccl_addr_space RNG *rng,
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ShaderData *sd, ShaderData *emission_sd, float3 throughput, ccl_addr_space PathState *state,
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PathRadiance *L)
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{
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#ifdef __EMISSION__
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if(!(kernel_data.integrator.use_direct_light && (ccl_fetch(sd, flag) & SD_BSDF_HAS_EVAL)))
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return;
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/* sample illumination from lights to find path contribution */
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float light_t = path_state_rng_1D(kg, rng, state, PRNG_LIGHT);
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float light_u, light_v;
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path_state_rng_2D(kg, rng, state, PRNG_LIGHT_U, &light_u, &light_v);
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Ray light_ray;
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BsdfEval L_light;
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bool is_lamp;
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#ifdef __OBJECT_MOTION__
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light_ray.time = ccl_fetch(sd, time);
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#endif
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LightSample ls;
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if(light_sample(kg, light_t, light_u, light_v, ccl_fetch(sd, time), ccl_fetch(sd, P), state->bounce, &ls)) {
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if(direct_emission(kg, sd, emission_sd, &ls, state, &light_ray, &L_light, &is_lamp)) {
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/* trace shadow ray */
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float3 shadow;
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if(!shadow_blocked(kg, emission_sd, state, &light_ray, &shadow)) {
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/* accumulate */
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path_radiance_accum_light(L, throughput, &L_light, shadow, 1.0f, state->bounce, is_lamp);
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}
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}
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}
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#endif
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}
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#endif
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/* path tracing: bounce off or through surface to with new direction stored in ray */
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ccl_device bool kernel_path_surface_bounce(KernelGlobals *kg,
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ccl_addr_space RNG *rng,
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ShaderData *sd,
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ccl_addr_space float3 *throughput,
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ccl_addr_space PathState *state,
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PathRadiance *L,
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ccl_addr_space Ray *ray)
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{
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/* no BSDF? we can stop here */
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if(ccl_fetch(sd, flag) & SD_BSDF) {
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/* sample BSDF */
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float bsdf_pdf;
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BsdfEval bsdf_eval;
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float3 bsdf_omega_in;
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differential3 bsdf_domega_in;
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float bsdf_u, bsdf_v;
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path_state_rng_2D(kg, rng, state, PRNG_BSDF_U, &bsdf_u, &bsdf_v);
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int label;
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label = shader_bsdf_sample(kg, sd, bsdf_u, bsdf_v, &bsdf_eval,
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&bsdf_omega_in, &bsdf_domega_in, &bsdf_pdf);
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if(bsdf_pdf == 0.0f || bsdf_eval_is_zero(&bsdf_eval))
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return false;
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/* modify throughput */
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path_radiance_bsdf_bounce(L, throughput, &bsdf_eval, bsdf_pdf, state->bounce, label);
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/* set labels */
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if(!(label & LABEL_TRANSPARENT)) {
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state->ray_pdf = bsdf_pdf;
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#ifdef __LAMP_MIS__
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state->ray_t = 0.0f;
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#endif
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state->min_ray_pdf = fminf(bsdf_pdf, state->min_ray_pdf);
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}
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/* update path state */
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path_state_next(kg, state, label);
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/* setup ray */
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ray->P = ray_offset(ccl_fetch(sd, P), (label & LABEL_TRANSMIT)? -ccl_fetch(sd, Ng): ccl_fetch(sd, Ng));
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ray->D = normalize(bsdf_omega_in);
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if(state->bounce == 0)
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ray->t -= ccl_fetch(sd, ray_length); /* clipping works through transparent */
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else
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ray->t = FLT_MAX;
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#ifdef __RAY_DIFFERENTIALS__
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ray->dP = ccl_fetch(sd, dP);
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ray->dD = bsdf_domega_in;
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#endif
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#ifdef __VOLUME__
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/* enter/exit volume */
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if(label & LABEL_TRANSMIT)
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kernel_volume_stack_enter_exit(kg, sd, state->volume_stack);
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#endif
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return true;
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}
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#ifdef __VOLUME__
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else if(ccl_fetch(sd, flag) & SD_HAS_ONLY_VOLUME) {
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/* no surface shader but have a volume shader? act transparent */
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/* update path state, count as transparent */
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path_state_next(kg, state, LABEL_TRANSPARENT);
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if(state->bounce == 0)
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ray->t -= ccl_fetch(sd, ray_length); /* clipping works through transparent */
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else
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ray->t = FLT_MAX;
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/* setup ray position, direction stays unchanged */
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ray->P = ray_offset(ccl_fetch(sd, P), -ccl_fetch(sd, Ng));
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#ifdef __RAY_DIFFERENTIALS__
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ray->dP = ccl_fetch(sd, dP);
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#endif
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/* enter/exit volume */
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kernel_volume_stack_enter_exit(kg, sd, state->volume_stack);
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return true;
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}
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#endif
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else {
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/* no bsdf or volume? */
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return false;
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}
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}
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CCL_NAMESPACE_END
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