Brecht Van Lommel
0df9b2c715
It is basically brute force volume scattering within the mesh, but part of the SSS code for faster performance. The main difference with actual volume scattering is that we assume the boundaries are diffuse and that all lighting is coming through this boundary from outside the volume. This gives much more accurate results for thin features and low density. Some challenges remain however: * Significantly more noisy than BSSRDF. Adding Dwivedi sampling may help here, but it's unclear still how much it helps in real world cases. * Due to this being a volumetric method, geometry like eyes or mouth can darken the skin on the outside. We may be able to reduce this effect, or users can compensate for it by reducing the scattering radius in such areas. * Sharp corners are quite bright. This matches actual volume rendering and results in some other renderers, but maybe not so much real world objects. Differential Revision: https://developer.blender.org/D3054
307 lines
12 KiB
C++
307 lines
12 KiB
C++
/*
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* Copyright 2011-2017 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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ccl_device_inline void kernel_split_branched_path_subsurface_indirect_light_init(KernelGlobals *kg, int ray_index)
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{
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kernel_split_branched_path_indirect_loop_init(kg, ray_index);
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SplitBranchedState *branched_state = &kernel_split_state.branched_state[ray_index];
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branched_state->ss_next_closure = 0;
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branched_state->ss_next_sample = 0;
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branched_state->num_hits = 0;
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branched_state->next_hit = 0;
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ADD_RAY_FLAG(kernel_split_state.ray_state, ray_index, RAY_BRANCHED_SUBSURFACE_INDIRECT);
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}
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ccl_device_noinline bool kernel_split_branched_path_subsurface_indirect_light_iter(KernelGlobals *kg, int ray_index)
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{
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SplitBranchedState *branched_state = &kernel_split_state.branched_state[ray_index];
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ShaderData *sd = kernel_split_sd(branched_state_sd, ray_index);
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PathRadiance *L = &kernel_split_state.path_radiance[ray_index];
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ShaderData *emission_sd = AS_SHADER_DATA(&kernel_split_state.sd_DL_shadow[ray_index]);
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for(int i = branched_state->ss_next_closure; i < sd->num_closure; i++) {
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ShaderClosure *sc = &sd->closure[i];
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if(!CLOSURE_IS_BSSRDF(sc->type))
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continue;
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/* set up random number generator */
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if(branched_state->ss_next_sample == 0 && branched_state->next_hit == 0 &&
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branched_state->next_closure == 0 && branched_state->next_sample == 0)
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{
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branched_state->lcg_state = lcg_state_init_addrspace(&branched_state->path_state,
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0x68bc21eb);
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}
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int num_samples = kernel_data.integrator.subsurface_samples * 3;
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float num_samples_inv = 1.0f/num_samples;
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uint bssrdf_rng_hash = cmj_hash(branched_state->path_state.rng_hash, i);
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/* do subsurface scatter step with copy of shader data, this will
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* replace the BSSRDF with a diffuse BSDF closure */
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for(int j = branched_state->ss_next_sample; j < num_samples; j++) {
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ccl_global PathState *hit_state = &kernel_split_state.path_state[ray_index];
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*hit_state = branched_state->path_state;
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hit_state->rng_hash = bssrdf_rng_hash;
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path_state_branch(hit_state, j, num_samples);
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ccl_global LocalIntersection *ss_isect = &branched_state->ss_isect;
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float bssrdf_u, bssrdf_v;
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path_branched_rng_2D(kg,
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bssrdf_rng_hash,
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hit_state,
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j,
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num_samples,
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PRNG_BSDF_U,
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&bssrdf_u,
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&bssrdf_v);
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/* intersection is expensive so avoid doing multiple times for the same input */
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if(branched_state->next_hit == 0 && branched_state->next_closure == 0 && branched_state->next_sample == 0) {
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uint lcg_state = branched_state->lcg_state;
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LocalIntersection ss_isect_private;
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branched_state->num_hits = subsurface_scatter_multi_intersect(kg,
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&ss_isect_private,
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sd,
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hit_state,
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sc,
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&lcg_state,
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bssrdf_u, bssrdf_v,
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true);
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branched_state->lcg_state = lcg_state;
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*ss_isect = ss_isect_private;
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}
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hit_state->rng_offset += PRNG_BOUNCE_NUM;
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#ifdef __VOLUME__
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Ray volume_ray = branched_state->ray;
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bool need_update_volume_stack =
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kernel_data.integrator.use_volumes &&
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sd->object_flag & SD_OBJECT_INTERSECTS_VOLUME;
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#endif /* __VOLUME__ */
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/* compute lighting with the BSDF closure */
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for(int hit = branched_state->next_hit; hit < branched_state->num_hits; hit++) {
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ShaderData *bssrdf_sd = kernel_split_sd(sd, ray_index);
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*bssrdf_sd = *sd; /* note: copy happens each iteration of inner loop, this is
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* important as the indirect path will write into bssrdf_sd */
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LocalIntersection ss_isect_private = *ss_isect;
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subsurface_scatter_multi_setup(kg,
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&ss_isect_private,
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hit,
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bssrdf_sd,
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hit_state,
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sc);
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*ss_isect = ss_isect_private;
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#ifdef __VOLUME__
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if(need_update_volume_stack) {
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/* Setup ray from previous surface point to the new one. */
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float3 P = ray_offset(bssrdf_sd->P, -bssrdf_sd->Ng);
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volume_ray.D = normalize_len(P - volume_ray.P, &volume_ray.t);
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for(int k = 0; k < VOLUME_STACK_SIZE; k++) {
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hit_state->volume_stack[k] = branched_state->path_state.volume_stack[k];
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}
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kernel_volume_stack_update_for_subsurface(kg,
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emission_sd,
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&volume_ray,
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hit_state->volume_stack);
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}
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#endif /* __VOLUME__ */
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#ifdef __EMISSION__
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if(branched_state->next_closure == 0 && branched_state->next_sample == 0) {
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/* direct light */
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if(kernel_data.integrator.use_direct_light) {
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int all = (kernel_data.integrator.sample_all_lights_direct) ||
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(hit_state->flag & PATH_RAY_SHADOW_CATCHER);
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kernel_branched_path_surface_connect_light(kg,
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bssrdf_sd,
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emission_sd,
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hit_state,
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branched_state->throughput,
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num_samples_inv,
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L,
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all);
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}
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}
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#endif /* __EMISSION__ */
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/* indirect light */
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if(kernel_split_branched_path_surface_indirect_light_iter(kg,
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ray_index,
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num_samples_inv,
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bssrdf_sd,
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false,
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false))
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{
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branched_state->ss_next_closure = i;
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branched_state->ss_next_sample = j;
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branched_state->next_hit = hit;
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return true;
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}
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branched_state->next_closure = 0;
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}
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branched_state->next_hit = 0;
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}
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branched_state->ss_next_sample = 0;
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}
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branched_state->ss_next_closure = sd->num_closure;
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branched_state->waiting_on_shared_samples = (branched_state->shared_sample_count > 0);
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if(branched_state->waiting_on_shared_samples) {
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return true;
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}
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kernel_split_branched_path_indirect_loop_end(kg, ray_index);
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return false;
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}
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#endif /* __BRANCHED_PATH__ && __SUBSURFACE__ */
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ccl_device void kernel_subsurface_scatter(KernelGlobals *kg)
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{
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int thread_index = ccl_global_id(1) * ccl_global_size(0) + ccl_global_id(0);
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if(thread_index == 0) {
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/* We will empty both queues in this kernel. */
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kernel_split_params.queue_index[QUEUE_ACTIVE_AND_REGENERATED_RAYS] = 0;
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kernel_split_params.queue_index[QUEUE_HITBG_BUFF_UPDATE_TOREGEN_RAYS] = 0;
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}
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int ray_index = ccl_global_id(1) * ccl_global_size(0) + ccl_global_id(0);
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ray_index = get_ray_index(kg, ray_index,
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QUEUE_ACTIVE_AND_REGENERATED_RAYS,
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kernel_split_state.queue_data,
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kernel_split_params.queue_size,
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1);
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get_ray_index(kg, thread_index,
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QUEUE_HITBG_BUFF_UPDATE_TOREGEN_RAYS,
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kernel_split_state.queue_data,
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kernel_split_params.queue_size,
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1);
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#ifdef __SUBSURFACE__
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ccl_global char *ray_state = kernel_split_state.ray_state;
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if(IS_STATE(ray_state, ray_index, RAY_ACTIVE)) {
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ccl_global PathState *state = &kernel_split_state.path_state[ray_index];
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PathRadiance *L = &kernel_split_state.path_radiance[ray_index];
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ccl_global Ray *ray = &kernel_split_state.ray[ray_index];
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ccl_global float3 *throughput = &kernel_split_state.throughput[ray_index];
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ccl_global SubsurfaceIndirectRays *ss_indirect = &kernel_split_state.ss_rays[ray_index];
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ShaderData *sd = kernel_split_sd(sd, ray_index);
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ShaderData *emission_sd = AS_SHADER_DATA(&kernel_split_state.sd_DL_shadow[ray_index]);
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if(sd->flag & SD_BSSRDF) {
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#ifdef __BRANCHED_PATH__
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if(!kernel_data.integrator.branched) {
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#endif
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if(kernel_path_subsurface_scatter(kg,
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sd,
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emission_sd,
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L,
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state,
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ray,
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throughput,
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ss_indirect))
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{
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kernel_split_path_end(kg, ray_index);
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}
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#ifdef __BRANCHED_PATH__
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}
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else if(IS_FLAG(ray_state, ray_index, RAY_BRANCHED_INDIRECT)) {
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float bssrdf_u, bssrdf_v;
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path_state_rng_2D(kg,
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state,
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PRNG_BSDF_U,
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&bssrdf_u, &bssrdf_v);
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const ShaderClosure *sc = shader_bssrdf_pick(sd, throughput, &bssrdf_u);
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/* do bssrdf scatter step if we picked a bssrdf closure */
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if(sc) {
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uint lcg_state = lcg_state_init_addrspace(state, 0x68bc21eb);
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subsurface_scatter_step(kg,
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sd,
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state,
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sc,
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&lcg_state,
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bssrdf_u, bssrdf_v,
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false);
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}
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}
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else {
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kernel_split_branched_path_subsurface_indirect_light_init(kg, ray_index);
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if(kernel_split_branched_path_subsurface_indirect_light_iter(kg, ray_index)) {
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ASSIGN_RAY_STATE(ray_state, ray_index, RAY_REGENERATED);
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}
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}
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#endif
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}
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}
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# ifdef __BRANCHED_PATH__
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if(ccl_global_id(0) == 0 && ccl_global_id(1) == 0) {
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kernel_split_params.queue_index[QUEUE_SUBSURFACE_INDIRECT_ITER] = 0;
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}
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/* iter loop */
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ray_index = get_ray_index(kg, ccl_global_id(1) * ccl_global_size(0) + ccl_global_id(0),
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QUEUE_SUBSURFACE_INDIRECT_ITER,
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kernel_split_state.queue_data,
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kernel_split_params.queue_size,
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1);
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if(IS_STATE(ray_state, ray_index, RAY_SUBSURFACE_INDIRECT_NEXT_ITER)) {
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/* for render passes, sum and reset indirect light pass variables
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* for the next samples */
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path_radiance_sum_indirect(&kernel_split_state.path_radiance[ray_index]);
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path_radiance_reset_indirect(&kernel_split_state.path_radiance[ray_index]);
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if(kernel_split_branched_path_subsurface_indirect_light_iter(kg, ray_index)) {
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ASSIGN_RAY_STATE(ray_state, ray_index, RAY_REGENERATED);
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}
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}
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# endif /* __BRANCHED_PATH__ */
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#endif /* __SUBSURFACE__ */
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}
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CCL_NAMESPACE_END
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