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/* SPDX-License-Identifier: Apache-2.0
* Copyright 2011-2022 Blender Foundation */
#pragma once
CCL_NAMESPACE_BEGIN
/* Volumetric read/write lambda functions - default implementations */
#ifndef VOLUME_READ_LAMBDA
# define VOLUME_READ_LAMBDA(function_call) \
auto volume_read_lambda_pass = [=](const int i) { return function_call; };
# define VOLUME_WRITE_LAMBDA(function_call) \
auto volume_write_lambda_pass = [=](const int i, VolumeStack entry) { function_call; };
#endif
/* Volume Stack
*
* This is an array of object/shared ID's that the current segment of the path
* is inside of. */
template<typename StackReadOp, typename StackWriteOp>
ccl_device void volume_stack_enter_exit(KernelGlobals kg,
ccl_private const ShaderData *sd,
StackReadOp stack_read,
StackWriteOp stack_write)
{
/* todo: we should have some way for objects to indicate if they want the
* world shader to work inside them. excluding it by default is problematic
* because non-volume objects can't be assumed to be closed manifolds */
if (!(sd->flag & SD_HAS_VOLUME)) {
return;
}
if (sd->flag & SD_BACKFACING) {
/* Exit volume object: remove from stack. */
for (int i = 0;; i++) {
VolumeStack entry = stack_read(i);
if (entry.shader == SHADER_NONE) {
break;
}
if (entry.object == sd->object) {
/* Shift back next stack entries. */
do {
entry = stack_read(i + 1);
stack_write(i, entry);
i++;
} while (entry.shader != SHADER_NONE);
return;
}
}
}
else {
/* Enter volume object: add to stack. */
int i;
for (i = 0;; i++) {
VolumeStack entry = stack_read(i);
if (entry.shader == SHADER_NONE) {
break;
}
/* Already in the stack? then we have nothing to do. */
if (entry.object == sd->object) {
return;
}
}
/* If we exceed the stack limit, ignore. */
if (i >= kernel_data.volume_stack_size - 1) {
return;
}
/* Add to the end of the stack. */
const VolumeStack new_entry = {sd->object, sd->shader};
const VolumeStack empty_entry = {OBJECT_NONE, SHADER_NONE};
stack_write(i, new_entry);
stack_write(i + 1, empty_entry);
}
}
ccl_device void volume_stack_enter_exit(KernelGlobals kg,
IntegratorState state,
ccl_private const ShaderData *sd)
{
VOLUME_READ_LAMBDA(integrator_state_read_volume_stack(state, i))
VOLUME_WRITE_LAMBDA(integrator_state_write_volume_stack(state, i, entry))
volume_stack_enter_exit(kg, sd, volume_read_lambda_pass, volume_write_lambda_pass);
}
ccl_device void shadow_volume_stack_enter_exit(KernelGlobals kg,
IntegratorShadowState state,
ccl_private const ShaderData *sd)
{
VOLUME_READ_LAMBDA(integrator_state_read_shadow_volume_stack(state, i))
VOLUME_WRITE_LAMBDA(integrator_state_write_shadow_volume_stack(state, i, entry))
volume_stack_enter_exit(kg, sd, volume_read_lambda_pass, volume_write_lambda_pass);
}
/* Clean stack after the last bounce.
*
* It is expected that all volumes are closed manifolds, so at the time when ray
* hits nothing (for example, it is a last bounce which goes to environment) the
* only expected volume in the stack is the world's one. All the rest volume
* entries should have been exited already.
*
* This isn't always true because of ray intersection precision issues, which
* could lead us to an infinite non-world volume in the stack, causing render
* artifacts.
*
* Use this function after the last bounce to get rid of all volumes apart from
* the world's one after the last bounce to avoid render artifacts.
*/
ccl_device_inline void volume_stack_clean(KernelGlobals kg, IntegratorState state)
{
if (kernel_data.background.volume_shader != SHADER_NONE) {
/* Keep the world's volume in stack. */
INTEGRATOR_STATE_ARRAY_WRITE(state, volume_stack, 1, shader) = SHADER_NONE;
}
else {
INTEGRATOR_STATE_ARRAY_WRITE(state, volume_stack, 0, shader) = SHADER_NONE;
}
}
template<typename StackReadOp>
ccl_device float volume_stack_step_size(KernelGlobals kg, StackReadOp stack_read)
{
float step_size = FLT_MAX;
for (int i = 0;; i++) {
VolumeStack entry = stack_read(i);
if (entry.shader == SHADER_NONE) {
break;
}
int shader_flag = kernel_data_fetch(shaders, (entry.shader & SHADER_MASK)).flags;
bool heterogeneous = false;
if (shader_flag & SD_HETEROGENEOUS_VOLUME) {
heterogeneous = true;
}
else if (shader_flag & SD_NEED_VOLUME_ATTRIBUTES) {
/* We want to render world or objects without any volume grids
* as homogeneous, but can only verify this at run-time since other
* heterogeneous volume objects may be using the same shader. */
int object = entry.object;
if (object != OBJECT_NONE) {
int object_flag = kernel_data_fetch(object_flag, object);
if (object_flag & SD_OBJECT_HAS_VOLUME_ATTRIBUTES) {
heterogeneous = true;
}
}
}
if (heterogeneous) {
float object_step_size = object_volume_step_size(kg, entry.object);
object_step_size *= kernel_data.integrator.volume_step_rate;
step_size = fminf(object_step_size, step_size);
}
}
return step_size;
}
typedef enum VolumeSampleMethod {
VOLUME_SAMPLE_NONE = 0,
VOLUME_SAMPLE_DISTANCE = (1 << 0),
VOLUME_SAMPLE_EQUIANGULAR = (1 << 1),
VOLUME_SAMPLE_MIS = (VOLUME_SAMPLE_DISTANCE | VOLUME_SAMPLE_EQUIANGULAR),
} VolumeSampleMethod;
ccl_device VolumeSampleMethod volume_stack_sample_method(KernelGlobals kg, IntegratorState state)
{
VolumeSampleMethod method = VOLUME_SAMPLE_NONE;
for (int i = 0;; i++) {
VolumeStack entry = integrator_state_read_volume_stack(state, i);
if (entry.shader == SHADER_NONE) {
break;
}
int shader_flag = kernel_data_fetch(shaders, (entry.shader & SHADER_MASK)).flags;
if (shader_flag & SD_VOLUME_MIS) {
/* Multiple importance sampling. */
return VOLUME_SAMPLE_MIS;
}
else if (shader_flag & SD_VOLUME_EQUIANGULAR) {
/* Distance + equiangular sampling -> multiple importance sampling. */
if (method == VOLUME_SAMPLE_DISTANCE) {
return VOLUME_SAMPLE_MIS;
}
/* Only equiangular sampling. */
method = VOLUME_SAMPLE_EQUIANGULAR;
}
else {
/* Distance + equiangular sampling -> multiple importance sampling. */
if (method == VOLUME_SAMPLE_EQUIANGULAR) {
return VOLUME_SAMPLE_MIS;
}
/* Distance sampling only. */
method = VOLUME_SAMPLE_DISTANCE;
}
}
return method;
}
CCL_NAMESPACE_END
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