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//! Light probes for baked global illumination.
use bevy_app::{App, Plugin};
use bevy_asset::{load_internal_asset, AssetId, Handle};
use bevy_core_pipeline::core_3d::Camera3d;
use bevy_derive::{Deref, DerefMut};
use bevy_ecs::{
component::Component,
entity::Entity,
query::With,
reflect::ReflectComponent,
schedule::IntoSystemConfigs,
system::{Commands, Local, Query, Res, ResMut, Resource},
};
use bevy_math::{Affine3A, Mat4, Vec3A, Vec4};
use bevy_reflect::{std_traits::ReflectDefault, Reflect};
use bevy_render::{
extract_instances::ExtractInstancesPlugin,
primitives::{Aabb, Frustum},
render_asset::RenderAssets,
render_resource::{DynamicUniformBuffer, Sampler, Shader, ShaderType, TextureView},
renderer::{RenderDevice, RenderQueue},
settings::WgpuFeatures,
texture::{FallbackImage, Image},
view::ExtractedView,
Extract, ExtractSchedule, Render, RenderApp, RenderSet,
};
use bevy_transform::prelude::GlobalTransform;
use bevy_utils::{tracing::error, FloatOrd, HashMap};
use std::hash::Hash;
use std::ops::Deref;
use crate::{
irradiance_volume::IRRADIANCE_VOLUME_SHADER_HANDLE,
light_probe::environment_map::{
EnvironmentMapIds, EnvironmentMapLight, ENVIRONMENT_MAP_SHADER_HANDLE,
},
};
use self::irradiance_volume::IrradianceVolume;
pub const LIGHT_PROBE_SHADER_HANDLE: Handle<Shader> = Handle::weak_from_u128(8954249792581071582);
pub mod environment_map;
pub mod irradiance_volume;
/// The maximum number of each type of light probe that each view will consider.
///
/// Because the fragment shader does a linear search through the list for each
/// fragment, this number needs to be relatively small.
pub const MAX_VIEW_LIGHT_PROBES: usize = 8;
/// How many texture bindings are used in the fragment shader, *not* counting
/// environment maps or irradiance volumes.
const STANDARD_MATERIAL_FRAGMENT_SHADER_MIN_TEXTURE_BINDINGS: usize = 16;
/// Adds support for light probes: cuboid bounding regions that apply global
/// illumination to objects within them.
///
/// This also adds support for view environment maps: diffuse and specular
/// cubemaps applied to all objects that a view renders.
pub struct LightProbePlugin;
/// A marker component for a light probe, which is a cuboid region that provides
/// global illumination to all fragments inside it.
///
/// The light probe range is conceptually a unit cube (1×1×1) centered on the
/// origin. The [`bevy_transform::prelude::Transform`] applied to this entity
/// can scale, rotate, or translate that cube so that it contains all fragments
/// that should take this light probe into account.
///
/// Note that a light probe will have no effect unless the entity contains some
/// kind of illumination, which can either be an [`EnvironmentMapLight`] or an
/// [`IrradianceVolume`].
///
/// When multiple sources of indirect illumination can be applied to a fragment,
/// the highest-quality one is chosen. Diffuse and specular illumination are
/// considered separately, so, for example, Bevy may decide to sample the
/// diffuse illumination from an irradiance volume and the specular illumination
/// from a reflection probe. From highest priority to lowest priority, the
/// ranking is as follows:
///
/// | Rank | Diffuse | Specular |
/// | ---- | -------------------- | -------------------- |
/// | 1 | Lightmap | Lightmap |
/// | 2 | Irradiance volume | Reflection probe |
/// | 3 | Reflection probe | View environment map |
/// | 4 | View environment map | |
///
/// Note that ambient light is always added to the diffuse component and does
/// not participate in the ranking. That is, ambient light is applied in
/// addition to, not instead of, the light sources above.
///
/// A terminology note: Unfortunately, there is little agreement across game and
/// graphics engines as to what to call the various techniques that Bevy groups
/// under the term *light probe*. In Bevy, a *light probe* is the generic term
/// that encompasses both *reflection probes* and *irradiance volumes*. In
/// object-oriented terms, *light probe* is the superclass, and *reflection
/// probe* and *irradiance volume* are subclasses. In other engines, you may see
/// the term *light probe* refer to an irradiance volume with a single voxel, or
/// perhaps some other technique, while in Bevy *light probe* refers not to a
/// specific technique but rather to a class of techniques. Developers familiar
/// with other engines should be aware of this terminology difference.
#[derive(Component, Debug, Clone, Copy, Default, Reflect)]
#[reflect(Component, Default)]
pub struct LightProbe;
/// A GPU type that stores information about a light probe.
#[derive(Clone, Copy, ShaderType, Default)]
struct RenderLightProbe {
/// The transform from the world space to the model space. This is used to
/// efficiently check for bounding box intersection.
inverse_transpose_transform: [Vec4; 3],
/// The index of the texture or textures in the appropriate binding array or
/// arrays.
///
/// For example, for reflection probes this is the index of the cubemap in
/// the diffuse and specular texture arrays.
texture_index: i32,
/// Scale factor applied to the light generated by this light probe.
///
/// See the comment in [`EnvironmentMapLight`] for details.
intensity: f32,
}
/// A per-view shader uniform that specifies all the light probes that the view
/// takes into account.
#[derive(ShaderType)]
pub struct LightProbesUniform {
/// The list of applicable reflection probes, sorted from nearest to the
/// camera to the farthest away from the camera.
reflection_probes: [RenderLightProbe; MAX_VIEW_LIGHT_PROBES],
/// The list of applicable irradiance volumes, sorted from nearest to the
/// camera to the farthest away from the camera.
irradiance_volumes: [RenderLightProbe; MAX_VIEW_LIGHT_PROBES],
/// The number of reflection probes in the list.
reflection_probe_count: i32,
/// The number of irradiance volumes in the list.
irradiance_volume_count: i32,
/// The index of the diffuse and specular environment maps associated with
/// the view itself. This is used as a fallback if no reflection probe in
/// the list contains the fragment.
view_cubemap_index: i32,
/// The smallest valid mipmap level for the specular environment cubemap
/// associated with the view.
smallest_specular_mip_level_for_view: u32,
/// The intensity of the environment cubemap associated with the view.
///
/// See the comment in [`EnvironmentMapLight`] for details.
intensity_for_view: f32,
}
/// A GPU buffer that stores information about all light probes.
#[derive(Resource, Default, Deref, DerefMut)]
pub struct LightProbesBuffer(DynamicUniformBuffer<LightProbesUniform>);
/// A component attached to each camera in the render world that stores the
/// index of the [`LightProbesUniform`] in the [`LightProbesBuffer`].
#[derive(Component, Default, Deref, DerefMut)]
pub struct ViewLightProbesUniformOffset(u32);
/// Information that [`gather_light_probes`] keeps about each light probe.
///
/// This information is parameterized by the [`LightProbeComponent`] type. This
/// will either be [`EnvironmentMapLight`] for reflection probes or
/// [`IrradianceVolume`] for irradiance volumes.
#[allow(dead_code)]
struct LightProbeInfo<C>
where
C: LightProbeComponent,
{
// The transform from world space to light probe space.
inverse_transform: Mat4,
// The transform from light probe space to world space.
affine_transform: Affine3A,
// Scale factor applied to the diffuse and specular light generated by this
// reflection probe.
//
// See the comment in [`EnvironmentMapLight`] for details.
intensity: f32,
// The IDs of all assets associated with this light probe.
//
// Because each type of light probe component may reference different types
// of assets (e.g. a reflection probe references two cubemap assets while an
// irradiance volume references a single 3D texture asset), this is generic.
asset_id: C::AssetId,
}
/// A component, part of the render world, that stores the mapping from asset ID
/// or IDs to the texture index in the appropriate binding arrays.
///
/// Cubemap textures belonging to environment maps are collected into binding
/// arrays, and the index of each texture is presented to the shader for runtime
/// lookup. 3D textures belonging to reflection probes are likewise collected
/// into binding arrays, and the shader accesses the 3D texture by index.
///
/// This component is attached to each view in the render world, because each
/// view may have a different set of light probes that it considers and therefore
/// the texture indices are per-view.
#[derive(Component, Default)]
pub struct RenderViewLightProbes<C>
where
C: LightProbeComponent,
{
/// The list of environment maps presented to the shader, in order.
binding_index_to_textures: Vec<C::AssetId>,
/// The reverse of `binding_index_to_cubemap`: a map from the texture ID to
/// the index in `binding_index_to_cubemap`.
cubemap_to_binding_index: HashMap<C::AssetId, u32>,
/// Information about each light probe, ready for upload to the GPU, sorted
/// in order from closest to the camera to farthest.
///
/// Note that this is not necessarily ordered by binding index. So don't
/// write code like
/// `render_light_probes[cubemap_to_binding_index[asset_id]]`; instead
/// search for the light probe with the appropriate binding index in this
/// array.
render_light_probes: Vec<RenderLightProbe>,
/// Information needed to render the light probe attached directly to the
/// view, if applicable.
///
/// A light probe attached directly to a view represents a "global" light
/// probe that affects all objects not in the bounding region of any light
/// probe. Currently, the only light probe type that supports this is the
/// [`EnvironmentMapLight`].
view_light_probe_info: C::ViewLightProbeInfo,
}
/// A trait implemented by all components that represent light probes.
///
/// Currently, the two light probe types are [`EnvironmentMapLight`] and
/// [`IrradianceVolume`], for reflection probes and irradiance volumes
/// respectively.
///
/// Most light probe systems are written to be generic over the type of light
/// probe. This allows much of the code to be shared and enables easy addition
/// of more light probe types (e.g. real-time reflection planes) in the future.
pub trait LightProbeComponent: Send + Sync + Component + Sized {
/// Holds [`AssetId`]s of the texture or textures that this light probe
/// references.
///
/// This can just be [`AssetId`] if the light probe only references one
/// texture. If it references multiple textures, it will be a structure
/// containing those asset IDs.
type AssetId: Send + Sync + Clone + Eq + Hash;
/// If the light probe can be attached to the view itself (as opposed to a
/// cuboid region within the scene), this contains the information that will
/// be passed to the GPU in order to render it. Otherwise, this will be
/// `()`.
///
/// Currently, only reflection probes (i.e. [`EnvironmentMapLight`]) can be
/// attached directly to views.
type ViewLightProbeInfo: Send + Sync + Default;
/// Returns the asset ID or asset IDs of the texture or textures referenced
/// by this light probe.
fn id(&self, image_assets: &RenderAssets<Image>) -> Option<Self::AssetId>;
/// Returns the intensity of this light probe.
///
/// This is a scaling factor that will be multiplied by the value or values
/// sampled from the texture.
fn intensity(&self) -> f32;
/// Creates an instance of [`RenderViewLightProbes`] containing all the
/// information needed to render this light probe.
///
/// This is called for every light probe in view every frame.
fn create_render_view_light_probes(
view_component: Option<&Self>,
image_assets: &RenderAssets<Image>,
) -> RenderViewLightProbes<Self>;
}
impl LightProbe {
/// Creates a new light probe component.
#[inline]
pub fn new() -> Self {
Self
}
}
impl Plugin for LightProbePlugin {
fn build(&self, app: &mut App) {
load_internal_asset!(
app,
LIGHT_PROBE_SHADER_HANDLE,
"light_probe.wgsl",
Shader::from_wgsl
);
load_internal_asset!(
app,
ENVIRONMENT_MAP_SHADER_HANDLE,
"environment_map.wgsl",
Shader::from_wgsl
);
load_internal_asset!(
app,
IRRADIANCE_VOLUME_SHADER_HANDLE,
"irradiance_volume.wgsl",
Shader::from_wgsl
);
app.register_type::<LightProbe>()
.register_type::<EnvironmentMapLight>()
.register_type::<IrradianceVolume>();
}
fn finish(&self, app: &mut App) {
let Ok(render_app) = app.get_sub_app_mut(RenderApp) else {
return;
};
render_app
.add_plugins(ExtractInstancesPlugin::<EnvironmentMapIds>::new())
.init_resource::<LightProbesBuffer>()
.add_systems(ExtractSchedule, gather_light_probes::<EnvironmentMapLight>)
.add_systems(ExtractSchedule, gather_light_probes::<IrradianceVolume>)
.add_systems(
Render,
upload_light_probes.in_set(RenderSet::PrepareResources),
);
}
}
/// Gathers up all light probes of a single type in the scene and assigns them
/// to views, performing frustum culling and distance sorting in the process.
fn gather_light_probes<C>(
image_assets: Res<RenderAssets<Image>>,
light_probe_query: Extract<Query<(&GlobalTransform, &C), With<LightProbe>>>,
view_query: Extract<Query<(Entity, &GlobalTransform, &Frustum, Option<&C>), With<Camera3d>>>,
mut reflection_probes: Local<Vec<LightProbeInfo<C>>>,
mut view_reflection_probes: Local<Vec<LightProbeInfo<C>>>,
mut commands: Commands,
) where
C: LightProbeComponent,
{
// Create [`LightProbeInfo`] for every light probe in the scene.
reflection_probes.clear();
reflection_probes.extend(
light_probe_query
.iter()
.filter_map(|query_row| LightProbeInfo::new(query_row, &image_assets)),
);
// Build up the light probes uniform and the key table.
for (view_entity, view_transform, view_frustum, view_component) in view_query.iter() {
// Cull light probes outside the view frustum.
view_reflection_probes.clear();
view_reflection_probes.extend(
reflection_probes
.iter()
.filter(|light_probe_info| light_probe_info.frustum_cull(view_frustum))
.cloned(),
);
// Sort by distance to camera.
view_reflection_probes.sort_by_cached_key(|light_probe_info| {
light_probe_info.camera_distance_sort_key(view_transform)
});
// Create the light probes list.
let mut render_view_light_probes =
C::create_render_view_light_probes(view_component, &image_assets);
// Gather up the light probes in the list.
render_view_light_probes.maybe_gather_light_probes(&view_reflection_probes);
// Record the per-view light probes.
if render_view_light_probes.is_empty() {
commands
.get_or_spawn(view_entity)
.remove::<RenderViewLightProbes<C>>();
} else {
commands
.get_or_spawn(view_entity)
.insert(render_view_light_probes);
}
}
}
// A system that runs after [`gather_light_probes`] and populates the GPU
// uniforms with the results.
//
// Note that, unlike [`gather_light_probes`], this system is not generic over
// the type of light probe. It collects light probes of all types together into
// a single structure, ready to be passed to the shader.
fn upload_light_probes(
mut commands: Commands,
views: Query<Entity, With<ExtractedView>>,
mut light_probes_buffer: ResMut<LightProbesBuffer>,
mut view_light_probes_query: Query<(
Option<&RenderViewLightProbes<EnvironmentMapLight>>,
Option<&RenderViewLightProbes<IrradianceVolume>>,
)>,
render_device: Res<RenderDevice>,
render_queue: Res<RenderQueue>,
) {
// If there are no views, bail.
if views.is_empty() {
return;
}
// Initialize the uniform buffer writer.
let mut writer = light_probes_buffer
.get_writer(views.iter().len(), &render_device, &render_queue)
.unwrap();
// Process each view.
for view_entity in views.iter() {
let Ok((render_view_environment_maps, render_view_irradiance_volumes)) =
view_light_probes_query.get_mut(view_entity)
else {
error!("Failed to find `RenderViewLightProbes` for the view!");
continue;
};
// Initialize the uniform with only the view environment map, if there
// is one.
let mut light_probes_uniform = LightProbesUniform {
reflection_probes: [RenderLightProbe::default(); MAX_VIEW_LIGHT_PROBES],
irradiance_volumes: [RenderLightProbe::default(); MAX_VIEW_LIGHT_PROBES],
reflection_probe_count: render_view_environment_maps
.map(|maps| maps.len())
.unwrap_or_default()
.min(MAX_VIEW_LIGHT_PROBES) as i32,
irradiance_volume_count: render_view_irradiance_volumes
.map(|maps| maps.len())
.unwrap_or_default()
.min(MAX_VIEW_LIGHT_PROBES) as i32,
view_cubemap_index: render_view_environment_maps
.map(|maps| maps.view_light_probe_info.cubemap_index)
.unwrap_or(-1),
smallest_specular_mip_level_for_view: render_view_environment_maps
.map(|maps| maps.view_light_probe_info.smallest_specular_mip_level)
.unwrap_or(0),
intensity_for_view: render_view_environment_maps
.map(|maps| maps.view_light_probe_info.intensity)
.unwrap_or(1.0),
};
// Add any environment maps that [`gather_light_probes`] found to the
// uniform.
if let Some(render_view_environment_maps) = render_view_environment_maps {
render_view_environment_maps.add_to_uniform(
&mut light_probes_uniform.reflection_probes,
&mut light_probes_uniform.reflection_probe_count,
);
}
// Add any irradiance volumes that [`gather_light_probes`] found to the
// uniform.
if let Some(render_view_irradiance_volumes) = render_view_irradiance_volumes {
render_view_irradiance_volumes.add_to_uniform(
&mut light_probes_uniform.irradiance_volumes,
&mut light_probes_uniform.irradiance_volume_count,
);
}
// Queue the view's uniforms to be written to the GPU.
let uniform_offset = writer.write(&light_probes_uniform);
commands
.entity(view_entity)
.insert(ViewLightProbesUniformOffset(uniform_offset));
}
}
impl Default for LightProbesUniform {
fn default() -> Self {
Self {
reflection_probes: [RenderLightProbe::default(); MAX_VIEW_LIGHT_PROBES],
irradiance_volumes: [RenderLightProbe::default(); MAX_VIEW_LIGHT_PROBES],
reflection_probe_count: 0,
irradiance_volume_count: 0,
view_cubemap_index: -1,
smallest_specular_mip_level_for_view: 0,
intensity_for_view: 1.0,
}
}
}
impl<C> LightProbeInfo<C>
where
C: LightProbeComponent,
{
/// Given the set of light probe components, constructs and returns
/// [`LightProbeInfo`]. This is done for every light probe in the scene
/// every frame.
fn new(
(light_probe_transform, environment_map): (&GlobalTransform, &C),
image_assets: &RenderAssets<Image>,
) -> Option<LightProbeInfo<C>> {
environment_map.id(image_assets).map(|id| LightProbeInfo {
affine_transform: light_probe_transform.affine(),
inverse_transform: light_probe_transform.compute_matrix().inverse(),
asset_id: id,
intensity: environment_map.intensity(),
})
}
/// Returns true if this light probe is in the viewing frustum of the camera
/// or false if it isn't.
fn frustum_cull(&self, view_frustum: &Frustum) -> bool {
view_frustum.intersects_obb(
&Aabb {
center: Vec3A::default(),
half_extents: Vec3A::splat(0.5),
},
&self.affine_transform,
true,
false,
)
}
/// Returns the squared distance from this light probe to the camera,
/// suitable for distance sorting.
fn camera_distance_sort_key(&self, view_transform: &GlobalTransform) -> FloatOrd {
FloatOrd(
(self.affine_transform.translation - view_transform.translation_vec3a())
.length_squared(),
)
}
}
impl<C> RenderViewLightProbes<C>
where
C: LightProbeComponent,
{
/// Creates a new empty list of light probes.
fn new() -> RenderViewLightProbes<C> {
RenderViewLightProbes {
binding_index_to_textures: vec![],
cubemap_to_binding_index: HashMap::new(),
render_light_probes: vec![],
view_light_probe_info: C::ViewLightProbeInfo::default(),
}
}
/// Returns true if there are no light probes in the list.
pub(crate) fn is_empty(&self) -> bool {
self.binding_index_to_textures.is_empty()
}
/// Returns the number of light probes in the list.
pub(crate) fn len(&self) -> usize {
self.binding_index_to_textures.len()
}
/// Adds a cubemap to the list of bindings, if it wasn't there already, and
/// returns its index within that list.
pub(crate) fn get_or_insert_cubemap(&mut self, cubemap_id: &C::AssetId) -> u32 {
*self
.cubemap_to_binding_index
.entry((*cubemap_id).clone())
.or_insert_with(|| {
let index = self.binding_index_to_textures.len() as u32;
self.binding_index_to_textures.push((*cubemap_id).clone());
index
})
}
/// Adds all the light probes in this structure to the supplied array, which
/// is expected to be shipped to the GPU.
fn add_to_uniform(
&self,
render_light_probes: &mut [RenderLightProbe; MAX_VIEW_LIGHT_PROBES],
render_light_probe_count: &mut i32,
) {
render_light_probes[0..self.render_light_probes.len()]
.copy_from_slice(&self.render_light_probes[..]);
*render_light_probe_count = self.render_light_probes.len() as i32;
}
/// Gathers up all light probes of the given type in the scene and records
/// them in this structure.
fn maybe_gather_light_probes(&mut self, light_probes: &[LightProbeInfo<C>]) {
for light_probe in light_probes.iter().take(MAX_VIEW_LIGHT_PROBES) {
// Determine the index of the cubemap in the binding array.
let cubemap_index = self.get_or_insert_cubemap(&light_probe.asset_id);
// Transpose the inverse transform to compress the structure on the
// GPU (from 4 `Vec4`s to 3 `Vec4`s). The shader will transpose it
// to recover the original inverse transform.
let inverse_transpose_transform = light_probe.inverse_transform.transpose();
// Write in the light probe data.
self.render_light_probes.push(RenderLightProbe {
inverse_transpose_transform: [
inverse_transpose_transform.x_axis,
inverse_transpose_transform.y_axis,
inverse_transpose_transform.z_axis,
],
texture_index: cubemap_index as i32,
intensity: light_probe.intensity,
});
}
}
}
impl<C> Clone for LightProbeInfo<C>
where
C: LightProbeComponent,
{
fn clone(&self) -> Self {
Self {
inverse_transform: self.inverse_transform,
affine_transform: self.affine_transform,
intensity: self.intensity,
asset_id: self.asset_id.clone(),
}
}
}
/// Adds a diffuse or specular texture view to the `texture_views` list, and
/// populates `sampler` if this is the first such view.
pub(crate) fn add_cubemap_texture_view<'a>(
texture_views: &mut Vec<&'a <TextureView as Deref>::Target>,
sampler: &mut Option<&'a Sampler>,
image_id: AssetId<Image>,
images: &'a RenderAssets<Image>,
fallback_image: &'a FallbackImage,
) {
match images.get(image_id) {
None => {
// Use the fallback image if the cubemap isn't loaded yet.
texture_views.push(&*fallback_image.cube.texture_view);
}
Some(image) => {
// If this is the first texture view, populate `sampler`.
if sampler.is_none() {
*sampler = Some(&image.sampler);
}
texture_views.push(&*image.texture_view);
}
}
}
/// Many things can go wrong when attempting to use texture binding arrays
/// (a.k.a. bindless textures). This function checks for these pitfalls:
///
/// 1. If GLSL support is enabled at the feature level, then in debug mode
/// `naga_oil` will attempt to compile all shader modules under GLSL to check
/// validity of names, even if GLSL isn't actually used. This will cause a crash
/// if binding arrays are enabled, because binding arrays are currently
/// unimplemented in the GLSL backend of Naga. Therefore, we disable binding
/// arrays if the `shader_format_glsl` feature is present.
///
/// 2. If there aren't enough texture bindings available to accommodate all the
/// binding arrays, the driver will panic. So we also bail out if there aren't
/// enough texture bindings available in the fragment shader.
///
/// 3. If binding arrays aren't supported on the hardware, then we obviously
/// can't use them.
///
/// 4. If binding arrays are supported on the hardware, but they can only be
/// accessed by uniform indices, that's not good enough, and we bail out.
///
/// If binding arrays aren't usable, we disable reflection probes and limit the
/// number of irradiance volumes in the scene to 1.
pub(crate) fn binding_arrays_are_usable(render_device: &RenderDevice) -> bool {
!cfg!(feature = "shader_format_glsl")
&& render_device.limits().max_storage_textures_per_shader_stage
>= (STANDARD_MATERIAL_FRAGMENT_SHADER_MIN_TEXTURE_BINDINGS + MAX_VIEW_LIGHT_PROBES)
as u32
&& render_device.features().contains(
WgpuFeatures::TEXTURE_BINDING_ARRAY
| WgpuFeatures::SAMPLED_TEXTURE_AND_STORAGE_BUFFER_ARRAY_NON_UNIFORM_INDEXING,
)
}