forked from bartvdbraak/blender
288 lines
8.5 KiB
C
288 lines
8.5 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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#ifdef __SHADOW_RECORD_ALL__
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/* Shadow function to compute how much light is blocked, CPU variation.
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*
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* We trace a single ray. If it hits any opaque surface, or more than a given
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* number of transparent surfaces is hit, then we consider the geometry to be
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* entirely blocked. If not, all transparent surfaces will be recorded and we
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* will shade them one by one to determine how much light is blocked. This all
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* happens in one scene intersection function.
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*
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* Recording all hits works well in some cases but may be slower in others. If
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* we have many semi-transparent hairs, one intersection may be faster because
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* you'd be reinteresecting the same hairs a lot with each step otherwise. If
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* however there is mostly binary transparency then we may be recording many
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* unnecessary intersections when one of the first surfaces blocks all light.
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*
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* From tests in real scenes it seems the performance loss is either minimal,
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* or there is a performance increase anyway due to avoiding the need to send
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* two rays with transparent shadows.
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*
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* This is CPU only because of qsort, and malloc or high stack space usage to
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* record all these intersections. */
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ccl_device_noinline int shadow_intersections_compare(const void *a, const void *b)
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{
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const Intersection *isect_a = (const Intersection*)a;
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const Intersection *isect_b = (const Intersection*)b;
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if(isect_a->t < isect_b->t)
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return -1;
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else if(isect_a->t > isect_b->t)
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return 1;
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else
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return 0;
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}
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#define STACK_MAX_HITS 64
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ccl_device_inline bool shadow_blocked(KernelGlobals *kg, PathState *state, Ray *ray, float3 *shadow)
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{
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*shadow = make_float3(1.0f, 1.0f, 1.0f);
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if(ray->t == 0.0f)
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return false;
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bool blocked;
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if(kernel_data.integrator.transparent_shadows) {
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/* check transparent bounces here, for volume scatter which can do
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* lighting before surface path termination is checked */
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if(state->transparent_bounce >= kernel_data.integrator.transparent_max_bounce)
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return true;
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/* intersect to find an opaque surface, or record all transparent surface hits */
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Intersection hits_stack[STACK_MAX_HITS];
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Intersection *hits = hits_stack;
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uint max_hits = kernel_data.integrator.transparent_max_bounce - state->transparent_bounce - 1;
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/* prefer to use stack but use dynamic allocation if too deep max hits
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* we need max_hits + 1 storage space due to the logic in
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* scene_intersect_shadow_all which will first store and then check if
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* the limit is exceeded */
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if(max_hits + 1 > STACK_MAX_HITS)
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hits = (Intersection*)malloc(sizeof(Intersection)*(max_hits + 1));
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uint num_hits;
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blocked = scene_intersect_shadow_all(kg, ray, hits, max_hits, &num_hits);
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/* if no opaque surface found but we did find transparent hits, shade them */
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if(!blocked && num_hits > 0) {
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float3 throughput = make_float3(1.0f, 1.0f, 1.0f);
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float3 Pend = ray->P + ray->D*ray->t;
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float last_t = 0.0f;
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int bounce = state->transparent_bounce;
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Intersection *isect = hits;
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#ifdef __VOLUME__
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PathState ps = *state;
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#endif
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qsort(hits, num_hits, sizeof(Intersection), shadow_intersections_compare);
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for(int hit = 0; hit < num_hits; hit++, isect++) {
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/* adjust intersection distance for moving ray forward */
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float new_t = isect->t;
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isect->t -= last_t;
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/* skip hit if we did not move forward, step by step raytracing
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* would have skipped it as well then */
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if(last_t == new_t)
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continue;
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last_t = new_t;
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#ifdef __VOLUME__
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/* attenuation between last surface and next surface */
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if(ps.volume_stack[0].shader != SHADER_NONE) {
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Ray segment_ray = *ray;
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segment_ray.t = isect->t;
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kernel_volume_shadow(kg, &ps, &segment_ray, &throughput);
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}
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#endif
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/* setup shader data at surface */
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ShaderData sd;
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shader_setup_from_ray(kg, &sd, isect, ray, state->bounce+1, bounce);
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/* attenuation from transparent surface */
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if(!(sd.flag & SD_HAS_ONLY_VOLUME)) {
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shader_eval_surface(kg, &sd, 0.0f, PATH_RAY_SHADOW, SHADER_CONTEXT_SHADOW);
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throughput *= shader_bsdf_transparency(kg, &sd);
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}
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/* stop if all light is blocked */
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if(is_zero(throughput)) {
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/* free dynamic storage */
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if(hits != hits_stack)
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free(hits);
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return true;
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}
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/* move ray forward */
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ray->P = sd.P;
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if(ray->t != FLT_MAX)
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ray->D = normalize_len(Pend - ray->P, &ray->t);
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#ifdef __VOLUME__
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/* exit/enter volume */
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kernel_volume_stack_enter_exit(kg, &sd, ps.volume_stack);
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#endif
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bounce++;
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}
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#ifdef __VOLUME__
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/* attenuation for last line segment towards light */
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if(ps.volume_stack[0].shader != SHADER_NONE)
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kernel_volume_shadow(kg, &ps, ray, &throughput);
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#endif
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*shadow = throughput;
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if(hits != hits_stack)
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free(hits);
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return is_zero(throughput);
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}
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/* free dynamic storage */
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if(hits != hits_stack)
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free(hits);
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}
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else {
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Intersection isect;
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blocked = scene_intersect(kg, ray, PATH_RAY_SHADOW_OPAQUE, &isect, NULL, 0.0f, 0.0f);
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}
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#ifdef __VOLUME__
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if(!blocked && state->volume_stack[0].shader != SHADER_NONE) {
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/* apply attenuation from current volume shader */
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kernel_volume_shadow(kg, state, ray, shadow);
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}
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#endif
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return blocked;
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}
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#undef STACK_MAX_HITS
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#else
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/* Shadow function to compute how much light is blocked, GPU variation.
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*
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* Here we raytrace from one transparent surface to the next step by step.
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* To minimize overhead in cases where we don't need transparent shadows, we
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* first trace a regular shadow ray. We check if the hit primitive was
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* potentially transparent, and only in that case start marching. this gives
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* one extra ray cast for the cases were we do want transparency. */
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ccl_device_inline bool shadow_blocked(KernelGlobals *kg, PathState *state, Ray *ray, float3 *shadow)
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{
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*shadow = make_float3(1.0f, 1.0f, 1.0f);
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if(ray->t == 0.0f)
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return false;
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Intersection isect;
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bool blocked = scene_intersect(kg, ray, PATH_RAY_SHADOW_OPAQUE, &isect, NULL, 0.0f, 0.0f);
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#ifdef __TRANSPARENT_SHADOWS__
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if(blocked && kernel_data.integrator.transparent_shadows) {
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if(shader_transparent_shadow(kg, &isect)) {
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float3 throughput = make_float3(1.0f, 1.0f, 1.0f);
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float3 Pend = ray->P + ray->D*ray->t;
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int bounce = state->transparent_bounce;
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#ifdef __VOLUME__
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PathState ps = *state;
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#endif
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for(;;) {
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if(bounce >= kernel_data.integrator.transparent_max_bounce)
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return true;
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if(!scene_intersect(kg, ray, PATH_RAY_SHADOW_TRANSPARENT, &isect, NULL, 0.0f, 0.0f))
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{
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#ifdef __VOLUME__
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/* attenuation for last line segment towards light */
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if(ps.volume_stack[0].shader != SHADER_NONE)
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kernel_volume_shadow(kg, &ps, ray, &throughput);
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#endif
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*shadow *= throughput;
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return false;
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}
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if(!shader_transparent_shadow(kg, &isect))
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return true;
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#ifdef __VOLUME__
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/* attenuation between last surface and next surface */
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if(ps.volume_stack[0].shader != SHADER_NONE) {
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Ray segment_ray = *ray;
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segment_ray.t = isect.t;
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kernel_volume_shadow(kg, &ps, &segment_ray, &throughput);
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}
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#endif
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/* setup shader data at surface */
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ShaderData sd;
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shader_setup_from_ray(kg, &sd, &isect, ray, state->bounce+1, bounce);
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/* attenuation from transparent surface */
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if(!(sd.flag & SD_HAS_ONLY_VOLUME)) {
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shader_eval_surface(kg, &sd, 0.0f, PATH_RAY_SHADOW, SHADER_CONTEXT_SHADOW);
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throughput *= shader_bsdf_transparency(kg, &sd);
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}
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if(is_zero(throughput))
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return true;
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/* move ray forward */
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ray->P = ray_offset(sd.P, -sd.Ng);
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if(ray->t != FLT_MAX)
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ray->D = normalize_len(Pend - ray->P, &ray->t);
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#ifdef __VOLUME__
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/* exit/enter volume */
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kernel_volume_stack_enter_exit(kg, &sd, ps.volume_stack);
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#endif
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bounce++;
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}
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}
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}
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#ifdef __VOLUME__
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else if(!blocked && state->volume_stack[0].shader != SHADER_NONE) {
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/* apply attenuation from current volume shader */
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kernel_volume_shadow(kg, state, ray, shadow);
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}
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#endif
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#endif
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return blocked;
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}
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#endif
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CCL_NAMESPACE_END
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