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blender/intern/cycles/kernel/kernel_path_branched.h
Lukas Stockner 43b374e8c5 Cycles: Implement denoising option for reducing noise in the rendered image 
This commit contains the first part of the new Cycles denoising option,
which filters the resulting image using information gathered during rendering
to get rid of noise while preserving visual features as well as possible.

To use the option, enable it in the render layer options. The default settings
fit a wide range of scenes, but the user can tweak individual settings to
control the tradeoff between a noise-free image, image details, and calculation
time.

Note that the denoiser may still change in the future and that some features
are not implemented yet. The most important missing feature is animation
denoising, which uses information from multiple frames at once to produce a
flicker-free and smoother result. These features will be added in the future.

Finally, thanks to all the people who supported this project:

- Google (through the GSoC) and Theory Studios for sponsoring the development
- The authors of the papers I used for implementing the denoiser (more details
  on them will be included in the technical docs)
- The other Cycles devs for feedback on the code, especially Sergey for
  mentoring the GSoC project and Brecht for the code review!
- And of course the users who helped with testing, reported bugs and things
  that could and/or should work better!
2017-05-07 14:40:58 +02:00

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/*
* Copyright 2011-2013 Blender Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
CCL_NAMESPACE_BEGIN
#ifdef __BRANCHED_PATH__
ccl_device_inline void kernel_branched_path_ao(KernelGlobals *kg,
ShaderData *sd,
ShaderData *emission_sd,
PathRadiance *L,
ccl_addr_space PathState *state,
RNG *rng,
float3 throughput)
{
int num_samples = kernel_data.integrator.ao_samples;
float num_samples_inv = 1.0f/num_samples;
float ao_factor = kernel_data.background.ao_factor;
float3 ao_N;
float3 ao_bsdf = shader_bsdf_ao(kg, sd, ao_factor, &ao_N);
float3 ao_alpha = shader_bsdf_alpha(kg, sd);
for(int j = 0; j < num_samples; j++) {
float bsdf_u, bsdf_v;
path_branched_rng_2D(kg, rng, state, j, num_samples, PRNG_BSDF_U, &bsdf_u, &bsdf_v);
float3 ao_D;
float ao_pdf;
sample_cos_hemisphere(ao_N, bsdf_u, bsdf_v, &ao_D, &ao_pdf);
if(dot(sd->Ng, ao_D) > 0.0f && ao_pdf != 0.0f) {
Ray light_ray;
float3 ao_shadow;
light_ray.P = ray_offset(sd->P, sd->Ng);
light_ray.D = ao_D;
light_ray.t = kernel_data.background.ao_distance;
#ifdef __OBJECT_MOTION__
light_ray.time = sd->time;
#endif /* __OBJECT_MOTION__ */
light_ray.dP = sd->dP;
light_ray.dD = differential3_zero();
if(!shadow_blocked(kg, emission_sd, state, &light_ray, &ao_shadow)) {
path_radiance_accum_ao(L, state, throughput*num_samples_inv, ao_alpha, ao_bsdf, ao_shadow);
}
else {
path_radiance_accum_total_ao(L, state, throughput*num_samples_inv, ao_bsdf);
}
}
}
}
#ifndef __SPLIT_KERNEL__
/* bounce off surface and integrate indirect light */
ccl_device_noinline void kernel_branched_path_surface_indirect_light(KernelGlobals *kg,
RNG *rng, ShaderData *sd, ShaderData *indirect_sd, ShaderData *emission_sd,
float3 throughput, float num_samples_adjust, PathState *state, PathRadiance *L)
{
float sum_sample_weight = 0.0f;
#ifdef __DENOISING_FEATURES__
if(state->denoising_feature_weight > 0.0f) {
for(int i = 0; i < sd->num_closure; i++) {
const ShaderClosure *sc = &sd->closure[i];
/* transparency is not handled here, but in outer loop */
if(!CLOSURE_IS_BSDF(sc->type) || CLOSURE_IS_BSDF_TRANSPARENT(sc->type)) {
continue;
}
sum_sample_weight += sc->sample_weight;
}
}
else {
sum_sample_weight = 1.0f;
}
#endif /* __DENOISING_FEATURES__ */
for(int i = 0; i < sd->num_closure; i++) {
const ShaderClosure *sc = &sd->closure[i];
/* transparency is not handled here, but in outer loop */
if(!CLOSURE_IS_BSDF(sc->type) || CLOSURE_IS_BSDF_TRANSPARENT(sc->type)) {
continue;
}
int num_samples;
if(CLOSURE_IS_BSDF_DIFFUSE(sc->type))
num_samples = kernel_data.integrator.diffuse_samples;
else if(CLOSURE_IS_BSDF_BSSRDF(sc->type))
num_samples = 1;
else if(CLOSURE_IS_BSDF_GLOSSY(sc->type))
num_samples = kernel_data.integrator.glossy_samples;
else
num_samples = kernel_data.integrator.transmission_samples;
num_samples = ceil_to_int(num_samples_adjust*num_samples);
float num_samples_inv = num_samples_adjust/num_samples;
RNG bsdf_rng = cmj_hash(*rng, i);
for(int j = 0; j < num_samples; j++) {
PathState ps = *state;
float3 tp = throughput;
Ray bsdf_ray;
if(!kernel_branched_path_surface_bounce(kg,
&bsdf_rng,
sd,
sc,
j,
num_samples,
&tp,
&ps,
L,
&bsdf_ray,
sum_sample_weight))
{
continue;
}
kernel_path_indirect(kg,
indirect_sd,
emission_sd,
rng,
&bsdf_ray,
tp*num_samples_inv,
num_samples,
&ps,
L);
/* for render passes, sum and reset indirect light pass variables
* for the next samples */
path_radiance_sum_indirect(L);
path_radiance_reset_indirect(L);
}
}
}
#ifdef __SUBSURFACE__
ccl_device void kernel_branched_path_subsurface_scatter(KernelGlobals *kg,
ShaderData *sd,
ShaderData *indirect_sd,
ShaderData *emission_sd,
PathRadiance *L,
PathState *state,
RNG *rng,
Ray *ray,
float3 throughput)
{
for(int i = 0; i < sd->num_closure; i++) {
ShaderClosure *sc = &sd->closure[i];
if(!CLOSURE_IS_BSSRDF(sc->type))
continue;
/* set up random number generator */
uint lcg_state = lcg_state_init(rng, state->rng_offset, state->sample, 0x68bc21eb);
int num_samples = kernel_data.integrator.subsurface_samples;
float num_samples_inv = 1.0f/num_samples;
RNG bssrdf_rng = cmj_hash(*rng, i);
/* do subsurface scatter step with copy of shader data, this will
* replace the BSSRDF with a diffuse BSDF closure */
for(int j = 0; j < num_samples; j++) {
SubsurfaceIntersection ss_isect;
float bssrdf_u, bssrdf_v;
path_branched_rng_2D(kg, &bssrdf_rng, state, j, num_samples, PRNG_BSDF_U, &bssrdf_u, &bssrdf_v);
int num_hits = subsurface_scatter_multi_intersect(kg,
&ss_isect,
sd,
sc,
&lcg_state,
bssrdf_u, bssrdf_v,
true);
#ifdef __VOLUME__
Ray volume_ray = *ray;
bool need_update_volume_stack =
kernel_data.integrator.use_volumes &&
sd->object_flag & SD_OBJECT_INTERSECTS_VOLUME;
#endif /* __VOLUME__ */
/* compute lighting with the BSDF closure */
for(int hit = 0; hit < num_hits; hit++) {
ShaderData bssrdf_sd = *sd;
subsurface_scatter_multi_setup(kg,
&ss_isect,
hit,
&bssrdf_sd,
state,
state->flag,
sc,
true);
PathState hit_state = *state;
path_state_branch(&hit_state, j, num_samples);
#ifdef __VOLUME__
if(need_update_volume_stack) {
/* Setup ray from previous surface point to the new one. */
float3 P = ray_offset(bssrdf_sd.P, -bssrdf_sd.Ng);
volume_ray.D = normalize_len(P - volume_ray.P,
&volume_ray.t);
kernel_volume_stack_update_for_subsurface(
kg,
emission_sd,
&volume_ray,
hit_state.volume_stack);
}
#endif /* __VOLUME__ */
#ifdef __EMISSION__
/* direct light */
if(kernel_data.integrator.use_direct_light) {
int all = (kernel_data.integrator.sample_all_lights_direct) ||
(state->flag & PATH_RAY_SHADOW_CATCHER);
kernel_branched_path_surface_connect_light(
kg,
rng,
&bssrdf_sd,
emission_sd,
&hit_state,
throughput,
num_samples_inv,
L,
all);
}
#endif /* __EMISSION__ */
/* indirect light */
kernel_branched_path_surface_indirect_light(
kg,
rng,
&bssrdf_sd,
indirect_sd,
emission_sd,
throughput,
num_samples_inv,
&hit_state,
L);
}
}
}
}
#endif /* __SUBSURFACE__ */
ccl_device float kernel_branched_path_integrate(KernelGlobals *kg,
RNG *rng,
int sample,
Ray ray,
ccl_global float *buffer,
PathRadiance *L,
bool *is_shadow_catcher)
{
/* initialize */
float3 throughput = make_float3(1.0f, 1.0f, 1.0f);
float L_transparent = 0.0f;
path_radiance_init(L, kernel_data.film.use_light_pass);
/* shader data memory used for both volumes and surfaces, saves stack space */
ShaderData sd;
/* shader data used by emission, shadows, volume stacks, indirect path */
ShaderData emission_sd, indirect_sd;
PathState state;
path_state_init(kg, &emission_sd, &state, rng, sample, &ray);
#ifdef __KERNEL_DEBUG__
DebugData debug_data;
debug_data_init(&debug_data);
#endif /* __KERNEL_DEBUG__ */
/* Main Loop
* Here we only handle transparency intersections from the camera ray.
* Indirect bounces are handled in kernel_branched_path_surface_indirect_light().
*/
for(;;) {
/* intersect scene */
Intersection isect;
uint visibility = path_state_ray_visibility(kg, &state);
#ifdef __HAIR__
float difl = 0.0f, extmax = 0.0f;
uint lcg_state = 0;
if(kernel_data.bvh.have_curves) {
if(kernel_data.cam.resolution == 1) {
float3 pixdiff = ray.dD.dx + ray.dD.dy;
/*pixdiff = pixdiff - dot(pixdiff, ray.D)*ray.D;*/
difl = kernel_data.curve.minimum_width * len(pixdiff) * 0.5f;
}
extmax = kernel_data.curve.maximum_width;
lcg_state = lcg_state_init(rng, state.rng_offset, state.sample, 0x51633e2d);
}
bool hit = scene_intersect(kg, ray, visibility, &isect, &lcg_state, difl, extmax);
#else
bool hit = scene_intersect(kg, ray, visibility, &isect, NULL, 0.0f, 0.0f);
#endif /* __HAIR__ */
#ifdef __KERNEL_DEBUG__
debug_data.num_bvh_traversed_nodes += isect.num_traversed_nodes;
debug_data.num_bvh_traversed_instances += isect.num_traversed_instances;
debug_data.num_bvh_intersections += isect.num_intersections;
debug_data.num_ray_bounces++;
#endif /* __KERNEL_DEBUG__ */
#ifdef __VOLUME__
/* Sanitize volume stack. */
if(!hit) {
kernel_volume_clean_stack(kg, state.volume_stack);
}
/* volume attenuation, emission, scatter */
if(state.volume_stack[0].shader != SHADER_NONE) {
Ray volume_ray = ray;
volume_ray.t = (hit)? isect.t: FLT_MAX;
bool heterogeneous = volume_stack_is_heterogeneous(kg, state.volume_stack);
#ifdef __VOLUME_DECOUPLED__
/* decoupled ray marching only supported on CPU */
/* cache steps along volume for repeated sampling */
VolumeSegment volume_segment;
shader_setup_from_volume(kg, &sd, &volume_ray);
kernel_volume_decoupled_record(kg, &state,
&volume_ray, &sd, &volume_segment, heterogeneous);
/* direct light sampling */
if(volume_segment.closure_flag & SD_SCATTER) {
volume_segment.sampling_method = volume_stack_sampling_method(kg, state.volume_stack);
int all = kernel_data.integrator.sample_all_lights_direct;
kernel_branched_path_volume_connect_light(kg, rng, &sd,
&emission_sd, throughput, &state, L, all,
&volume_ray, &volume_segment);
/* indirect light sampling */
int num_samples = kernel_data.integrator.volume_samples;
float num_samples_inv = 1.0f/num_samples;
for(int j = 0; j < num_samples; j++) {
PathState ps = state;
Ray pray = ray;
float3 tp = throughput;
/* branch RNG state */
path_state_branch(&ps, j, num_samples);
/* scatter sample. if we use distance sampling and take just one
* sample for direct and indirect light, we could share this
* computation, but makes code a bit complex */
float rphase = path_state_rng_1D_for_decision(kg, rng, &ps, PRNG_PHASE);
float rscatter = path_state_rng_1D_for_decision(kg, rng, &ps, PRNG_SCATTER_DISTANCE);
VolumeIntegrateResult result = kernel_volume_decoupled_scatter(kg,
&ps, &pray, &sd, &tp, rphase, rscatter, &volume_segment, NULL, false);
(void)result;
kernel_assert(result == VOLUME_PATH_SCATTERED);
if(kernel_path_volume_bounce(kg,
rng,
&sd,
&tp,
&ps,
L,
&pray))
{
kernel_path_indirect(kg,
&indirect_sd,
&emission_sd,
rng,
&pray,
tp*num_samples_inv,
num_samples,
&ps,
L);
/* for render passes, sum and reset indirect light pass variables
* for the next samples */
path_radiance_sum_indirect(L);
path_radiance_reset_indirect(L);
}
}
}
/* emission and transmittance */
if(volume_segment.closure_flag & SD_EMISSION)
path_radiance_accum_emission(L, throughput, volume_segment.accum_emission, state.bounce);
throughput *= volume_segment.accum_transmittance;
/* free cached steps */
kernel_volume_decoupled_free(kg, &volume_segment);
#else
/* GPU: no decoupled ray marching, scatter probalistically */
int num_samples = kernel_data.integrator.volume_samples;
float num_samples_inv = 1.0f/num_samples;
/* todo: we should cache the shader evaluations from stepping
* through the volume, for now we redo them multiple times */
for(int j = 0; j < num_samples; j++) {
PathState ps = state;
Ray pray = ray;
float3 tp = throughput * num_samples_inv;
/* branch RNG state */
path_state_branch(&ps, j, num_samples);
VolumeIntegrateResult result = kernel_volume_integrate(
kg, &ps, &sd, &volume_ray, L, &tp, rng, heterogeneous);
#ifdef __VOLUME_SCATTER__
if(result == VOLUME_PATH_SCATTERED) {
/* todo: support equiangular, MIS and all light sampling.
* alternatively get decoupled ray marching working on the GPU */
kernel_path_volume_connect_light(kg, rng, &sd, &emission_sd, tp, &state, L);
if(kernel_path_volume_bounce(kg,
rng,
&sd,
&tp,
&ps,
L,
&pray))
{
kernel_path_indirect(kg,
&indirect_sd,
&emission_sd,
rng,
&pray,
tp,
num_samples,
&ps,
L);
/* for render passes, sum and reset indirect light pass variables
* for the next samples */
path_radiance_sum_indirect(L);
path_radiance_reset_indirect(L);
}
}
#endif /* __VOLUME_SCATTER__ */
}
/* todo: avoid this calculation using decoupled ray marching */
kernel_volume_shadow(kg, &emission_sd, &state, &volume_ray, &throughput);
#endif /* __VOLUME_DECOUPLED__ */
}
#endif /* __VOLUME__ */
if(!hit) {
/* eval background shader if nothing hit */
if(kernel_data.background.transparent) {
L_transparent += average(throughput);
#ifdef __PASSES__
if(!(kernel_data.film.pass_flag & PASS_BACKGROUND))
#endif /* __PASSES__ */
break;
}
#ifdef __BACKGROUND__
/* sample background shader */
float3 L_background = indirect_background(kg, &emission_sd, &state, &ray);
path_radiance_accum_background(L, &state, throughput, L_background);
#endif /* __BACKGROUND__ */
break;
}
/* setup shading */
shader_setup_from_ray(kg, &sd, &isect, &ray);
shader_eval_surface(kg, &sd, rng, &state, 0.0f, state.flag, SHADER_CONTEXT_MAIN);
shader_merge_closures(&sd);
#ifdef __SHADOW_TRICKS__
if((sd.object_flag & SD_OBJECT_SHADOW_CATCHER)) {
if(state.flag & PATH_RAY_CAMERA) {
state.flag |= (PATH_RAY_SHADOW_CATCHER | PATH_RAY_SHADOW_CATCHER_ONLY | PATH_RAY_STORE_SHADOW_INFO);
state.catcher_object = sd.object;
if(!kernel_data.background.transparent) {
L->shadow_color = indirect_background(kg, &emission_sd, &state, &ray);
}
}
}
else {
state.flag &= ~PATH_RAY_SHADOW_CATCHER_ONLY;
}
#endif /* __SHADOW_TRICKS__ */
/* holdout */
#ifdef __HOLDOUT__
if((sd.flag & SD_HOLDOUT) || (sd.object_flag & SD_OBJECT_HOLDOUT_MASK)) {
if(kernel_data.background.transparent) {
float3 holdout_weight;
if(sd.object_flag & SD_OBJECT_HOLDOUT_MASK) {
holdout_weight = make_float3(1.0f, 1.0f, 1.0f);
}
else {
holdout_weight = shader_holdout_eval(kg, &sd);
}
/* any throughput is ok, should all be identical here */
L_transparent += average(holdout_weight*throughput);
}
if(sd.object_flag & SD_OBJECT_HOLDOUT_MASK) {
break;
}
}
#endif /* __HOLDOUT__ */
/* holdout mask objects do not write data passes */
kernel_write_data_passes(kg, buffer, L, &sd, sample, &state, throughput);
#ifdef __EMISSION__
/* emission */
if(sd.flag & SD_EMISSION) {
float3 emission = indirect_primitive_emission(kg, &sd, isect.t, state.flag, state.ray_pdf);
path_radiance_accum_emission(L, throughput, emission, state.bounce);
}
#endif /* __EMISSION__ */
/* transparency termination */
if(state.flag & PATH_RAY_TRANSPARENT) {
/* path termination. this is a strange place to put the termination, it's
* mainly due to the mixed in MIS that we use. gives too many unneeded
* shader evaluations, only need emission if we are going to terminate */
float probability = path_state_terminate_probability(kg, &state, throughput);
if(probability == 0.0f) {
break;
}
else if(probability != 1.0f) {
float terminate = path_state_rng_1D_for_decision(kg, rng, &state, PRNG_TERMINATE);
if(terminate >= probability)
break;
throughput /= probability;
}
}
kernel_update_denoising_features(kg, &sd, &state, L);
#ifdef __AO__
/* ambient occlusion */
if(kernel_data.integrator.use_ambient_occlusion || (sd.flag & SD_AO)) {
kernel_branched_path_ao(kg, &sd, &emission_sd, L, &state, rng, throughput);
}
#endif /* __AO__ */
#ifdef __SUBSURFACE__
/* bssrdf scatter to a different location on the same object */
if(sd.flag & SD_BSSRDF) {
kernel_branched_path_subsurface_scatter(kg, &sd, &indirect_sd, &emission_sd,
L, &state, rng, &ray, throughput);
}
#endif /* __SUBSURFACE__ */
if(!(sd.flag & SD_HAS_ONLY_VOLUME)) {
PathState hit_state = state;
#ifdef __EMISSION__
/* direct light */
if(kernel_data.integrator.use_direct_light) {
int all = (kernel_data.integrator.sample_all_lights_direct) ||
(state.flag & PATH_RAY_SHADOW_CATCHER);
kernel_branched_path_surface_connect_light(kg, rng,
&sd, &emission_sd, &hit_state, throughput, 1.0f, L, all);
}
#endif /* __EMISSION__ */
/* indirect light */
kernel_branched_path_surface_indirect_light(kg, rng,
&sd, &indirect_sd, &emission_sd, throughput, 1.0f, &hit_state, L);
/* continue in case of transparency */
throughput *= shader_bsdf_transparency(kg, &sd);
if(is_zero(throughput))
break;
}
/* Update Path State */
state.flag |= PATH_RAY_TRANSPARENT;
state.transparent_bounce++;
ray.P = ray_offset(sd.P, -sd.Ng);
ray.t -= sd.ray_length; /* clipping works through transparent */
#ifdef __RAY_DIFFERENTIALS__
ray.dP = sd.dP;
ray.dD.dx = -sd.dI.dx;
ray.dD.dy = -sd.dI.dy;
#endif /* __RAY_DIFFERENTIALS__ */
#ifdef __VOLUME__
/* enter/exit volume */
kernel_volume_stack_enter_exit(kg, &sd, state.volume_stack);
#endif /* __VOLUME__ */
}
#ifdef __SHADOW_TRICKS__
*is_shadow_catcher = (state.flag & PATH_RAY_SHADOW_CATCHER);
#endif /* __SHADOW_TRICKS__ */
#ifdef __KERNEL_DEBUG__
kernel_write_debug_passes(kg, buffer, &state, &debug_data, sample);
#endif /* __KERNEL_DEBUG__ */
return 1.0f - L_transparent;
}
ccl_device void kernel_branched_path_trace(KernelGlobals *kg,
ccl_global float *buffer, ccl_global uint *rng_state,
int sample, int x, int y, int offset, int stride)
{
/* buffer offset */
int index = offset + x + y*stride;
int pass_stride = kernel_data.film.pass_stride;
rng_state += index;
buffer += index*pass_stride;
/* initialize random numbers and ray */
RNG rng;
Ray ray;
kernel_path_trace_setup(kg, rng_state, sample, x, y, &rng, &ray);
/* integrate */
PathRadiance L;
bool is_shadow_catcher;
if(ray.t != 0.0f) {
float alpha = kernel_branched_path_integrate(kg, &rng, sample, ray, buffer, &L, &is_shadow_catcher);
kernel_write_result(kg, buffer, sample, &L, alpha, is_shadow_catcher);
}
else {
kernel_write_result(kg, buffer, sample, NULL, 0.0f, false);
}
path_rng_end(kg, rng_state, rng);
}
#endif /* __SPLIT_KERNEL__ */
#endif /* __BRANCHED_PATH__ */
CCL_NAMESPACE_END
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