a7283fc1d5
The distance sampling is mostly based on weighted delta tracking from [Monte Carlo Methods for Volumetric Light Transport Simulation] (http://iliyan.com/publications/VolumeSTAR/VolumeSTAR_EG2018.pdf). The recursive Monte Carlo estimation of the Radiative Transfer Equation is \[\langle L \rangle=\frac{\bar T(x\rightarrow y)}{\bar p(x\rightarrow y)}(L_e+\sigma_s L_s + \sigma_n L).\] where \(\bar T(x\rightarrow y) = e^{-\bar\sigma\Vert x-y\Vert}\) is the majorant transmittance between points \(x\) and \(y\), \(p(x\rightarrow y) = \bar\sigma e^{-\bar\sigma\Vert x-y\Vert}\) is the probability of sampling point \(y\) from point \(x\) following exponential distribution. At each recursive step, we randomly pick one of the two events proportional to their weights: * If \(\xi < \frac{\sigma_s}{\sigma_s+\vert\sigma_n\vert}\), we sample scatter event and evaluate \(L_s\). * Otherwise, no real collision happens and we continue the recursive process. The emission \(L_e\) is evaluated at each step. This also removes some unused volume settings from the UI: * "Max Steps" is removed, because the step size is automatically specified by the volume octree. There is a hard-coded threshold `VOLUME_MAX_STEPS` to prevent numerical issues. * "Homogeneous" is automatically detected during density evaluation An option "Unbiased" is added to the UI. When enabled, densities above the majorant are clamped.
141 lines
3.9 KiB
C++
141 lines
3.9 KiB
C++
/* SPDX-FileCopyrightText: 2011-2022 Blender Foundation
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*
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* SPDX-License-Identifier: Apache-2.0 */
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#include "scene/background.h"
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#include "device/device.h"
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#include "scene/integrator.h"
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#include "scene/light.h"
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#include "scene/scene.h"
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#include "scene/shader.h"
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#include "scene/shader_graph.h"
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#include "scene/shader_nodes.h"
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#include "scene/stats.h"
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#include "util/math.h"
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#include "util/time.h"
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CCL_NAMESPACE_BEGIN
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NODE_DEFINE(Background)
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{
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NodeType *type = NodeType::add("background", create);
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SOCKET_BOOLEAN(use_shader, "Use Shader", true);
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SOCKET_UINT(visibility, "Visibility", PATH_RAY_ALL_VISIBILITY);
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SOCKET_BOOLEAN(transparent, "Transparent", false);
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SOCKET_BOOLEAN(transparent_glass, "Transparent Glass", false);
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SOCKET_FLOAT(transparent_roughness_threshold, "Transparent Roughness Threshold", 0.0f);
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SOCKET_NODE(shader, "Shader", Shader::get_node_type());
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SOCKET_STRING(lightgroup, "Light Group", ustring());
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return type;
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}
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Background::Background() : Node(get_node_type())
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{
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shader = nullptr;
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}
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Background::~Background()
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{
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dereference_all_used_nodes();
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}
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void Background::device_update(Device *device, DeviceScene *dscene, Scene *scene)
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{
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if (!is_modified()) {
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return;
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}
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const scoped_callback_timer timer([scene](double time) {
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if (scene->update_stats) {
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scene->update_stats->background.times.add_entry({"device_update", time});
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}
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});
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device_free(device, dscene);
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Shader *bg_shader = get_shader(scene);
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/* set shader index and transparent option */
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KernelBackground *kbackground = &dscene->data.background;
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kbackground->transparent = transparent;
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kbackground->surface_shader = scene->shader_manager->get_shader_id(bg_shader);
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if (transparent && transparent_glass) {
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/* Square twice, once for principled BSDF convention, and once for
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* faster comparison in kernel with anisotropic roughness. */
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kbackground->transparent_roughness_squared_threshold = sqr(
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sqr(transparent_roughness_threshold));
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}
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else {
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kbackground->transparent_roughness_squared_threshold = -1.0f;
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}
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if (bg_shader->has_volume) {
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kbackground->volume_shader = kbackground->surface_shader;
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}
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else {
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kbackground->volume_shader = SHADER_NONE;
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}
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/* No background node, make world shader invisible to all rays, to skip evaluation in kernel. */
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if (bg_shader->graph->nodes.size() <= 1) {
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kbackground->surface_shader |= SHADER_EXCLUDE_ANY;
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}
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/* Background present, check visibilities */
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else {
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if (!(visibility & PATH_RAY_DIFFUSE)) {
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kbackground->surface_shader |= SHADER_EXCLUDE_DIFFUSE;
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}
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if (!(visibility & PATH_RAY_GLOSSY)) {
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kbackground->surface_shader |= SHADER_EXCLUDE_GLOSSY;
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}
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if (!(visibility & PATH_RAY_TRANSMIT)) {
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kbackground->surface_shader |= SHADER_EXCLUDE_TRANSMIT;
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}
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if (!(visibility & PATH_RAY_VOLUME_SCATTER)) {
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kbackground->surface_shader |= SHADER_EXCLUDE_SCATTER;
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}
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if (!(visibility & PATH_RAY_CAMERA)) {
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kbackground->surface_shader |= SHADER_EXCLUDE_CAMERA;
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}
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}
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/* Light group. */
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auto it = scene->lightgroups.find(lightgroup);
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if (it != scene->lightgroups.end()) {
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kbackground->lightgroup = it->second;
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}
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else {
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kbackground->lightgroup = LIGHTGROUP_NONE;
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}
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clear_modified();
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}
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void Background::device_free(Device * /*device*/, DeviceScene * /*dscene*/) {}
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void Background::tag_update(Scene *scene)
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{
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Shader *bg_shader = get_shader(scene);
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if (bg_shader && bg_shader->is_modified()) {
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/* Tag as modified to update the KernelBackground visibility information.
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* We only tag the use_shader socket as modified as it is related to the shader
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* and to avoid doing unnecessary updates anywhere else. */
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tag_use_shader_modified();
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}
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}
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Shader *Background::get_shader(const Scene *scene)
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{
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return (use_shader) ? ((shader) ? shader : scene->default_background) : scene->default_empty;
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}
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CCL_NAMESPACE_END
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