forked from bartvdbraak/blender
Brecht Van Lommel
e369a5c485
This is the simplest possible volume rendering case, constant density inside the volume and no scattering or emission. My plan is to tweak, verify and commit more volume rendering effects one by one, doing it all at once makes it difficult to verify correctness and track down bugs. Documentation is here: http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Cycles/Materials/Volume Currently this hooks into path tracing in 3 ways, which should get us pretty far until we add more advanced light sampling. These 3 hooks are repeated in the path tracing, branched path tracing and transparent shadow code: * Determine active volume shader at start of the path * Change active volume shader on transmission through a surface * Light attenuation over line segments between camera, surfaces and background This is work by "storm", Stuart Broadfoot, Thomas Dinges and myself.
137 lines
4.0 KiB
C
137 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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CCL_NAMESPACE_BEGIN
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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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#ifdef __HAIR__
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bool result = scene_intersect(kg, ray, PATH_RAY_SHADOW_OPAQUE, &isect, NULL, 0.0f, 0.0f);
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#else
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bool result = scene_intersect(kg, ray, PATH_RAY_SHADOW_OPAQUE, &isect);
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#endif
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#ifdef __TRANSPARENT_SHADOWS__
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if(result && kernel_data.integrator.transparent_shadows) {
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/* transparent shadows work in such a way to try to minimize overhead
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* in cases where we don't need them. after a regular shadow ray is
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* cast we check if the hit primitive was potentially transparent, and
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* only in that case start marching. this gives on extra ray cast for
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* the cases were we do want transparency.
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*
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* also note that for this to work correct, multi close sampling must
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* be used, since we don't pass a random number to shader_eval_surface */
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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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int volume_shader = state->volume_shader;
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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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}
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else if(bounce >= kernel_data.integrator.transparent_min_bounce) {
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/* todo: get random number somewhere for probabilistic terminate */
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#if 0
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float probability = average(throughput);
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float terminate = 0.0f;
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if(terminate >= probability)
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return true;
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throughput /= probability;
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#endif
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}
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#ifdef __HAIR__
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if(!scene_intersect(kg, ray, PATH_RAY_SHADOW_TRANSPARENT, &isect, NULL, 0.0f, 0.0f)) {
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#else
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if(!scene_intersect(kg, ray, PATH_RAY_SHADOW_TRANSPARENT, &isect)) {
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#endif
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#ifdef __VOLUME__
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/* attenuation for last line segment towards light */
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if(volume_shader != SHADER_NO_ID)
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throughput *= kernel_volume_get_shadow_attenuation(kg, state, ray, volume_shader);
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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(volume_shader != SHADER_NO_ID) {
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Ray segment_ray = *ray;
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segment_ray.t = isect.t;
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throughput *= kernel_volume_get_shadow_attenuation(kg, state, &segment_ray, volume_shader);
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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);
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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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/* 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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if(sd.flag & SD_BACKFACING)
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volume_shader = kernel_data.background.volume_shader;
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else
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volume_shader = (sd.flag & SD_HAS_VOLUME)? sd.shader: SHADER_NO_ID;
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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(!result && state->volume_shader != SHADER_NO_ID) {
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/* apply attenuation from current volume shader */
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*shadow *= kernel_volume_get_shadow_attenuation(kg, state, ray, state->volume_shader);
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}
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#endif
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#endif
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return result;
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}
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CCL_NAMESPACE_END
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