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https://github.com/bevyengine/bevy
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![image](https://github.com/bevyengine/bevy/assets/47158642/dbb62645-f639-4f2b-b84b-26fd915c186d)
# Objective
- Add Screen space ambient occlusion (SSAO). SSAO approximates
small-scale, local occlusion of _indirect_ diffuse light between
objects. SSAO does not apply to direct lighting, such as point or
directional lights.
- This darkens creases, e.g. on staircases, and gives nice contact
shadows where objects meet, giving entities a more "grounded" feel.
- Closes https://github.com/bevyengine/bevy/issues/3632.
## Solution
- Implement the GTAO algorithm.
-
https://www.activision.com/cdn/research/Practical_Real_Time_Strategies_for_Accurate_Indirect_Occlusion_NEW%20VERSION_COLOR.pdf
-
https://blog.selfshadow.com/publications/s2016-shading-course/activision/s2016_pbs_activision_occlusion.pdf
- Source code heavily based on [Intel's
XeGTAO](0d177ce06b/Source/Rendering/Shaders/XeGTAO.hlsli
).
- Add an SSAO bevy example.
## Algorithm Overview
* Run a depth and normal prepass
* Create downscaled mips of the depth texture (preprocess_depths pass)
* GTAO pass - for each pixel, take several random samples from the
depth+normal buffers, reconstruct world position, raytrace in screen
space to estimate occlusion. Rather then doing completely random samples
on a hemisphere, you choose random _slices_ of the hemisphere, and then
can analytically compute the full occlusion of that slice. Also compute
edges based on depth differences here.
* Spatial denoise pass - bilateral blur, using edge detection to not
blur over edges. This is the final SSAO result.
* Main pass - if SSAO exists, sample the SSAO texture, and set occlusion
to be the minimum of ssao/material occlusion. This then feeds into the
rest of the PBR shader as normal.
---
## Future Improvements
- Maybe remove the low quality preset for now (too noisy)
- WebGPU fallback (see below)
- Faster depth->world position (see reverted code)
- Bent normals
- Try interleaved gradient noise or spatiotemporal blue noise
- Replace the spatial denoiser with a combined spatial+temporal denoiser
- Render at half resolution and use a bilateral upsample
- Better multibounce approximation
(https://drive.google.com/file/d/1SyagcEVplIm2KkRD3WQYSO9O0Iyi1hfy/view)
## Far-Future Performance Improvements
- F16 math (missing naga-wgsl support
https://github.com/gfx-rs/naga/issues/1884)
- Faster coordinate space conversion for normals
- Faster depth mipchain creation
(https://github.com/GPUOpen-Effects/FidelityFX-SPD) (wgpu/naga does not
currently support subgroup ops)
- Deinterleaved SSAO for better cache efficiency
(https://developer.nvidia.com/sites/default/files/akamai/gameworks/samples/DeinterleavedTexturing.pdf)
## Other Interesting Papers
- Visibility bitmask
(https://link.springer.com/article/10.1007/s00371-022-02703-y,
https://cdrinmatane.github.io/posts/cgspotlight-slides/)
- Screen space diffuse lighting
(https://github.com/Patapom/GodComplex/blob/master/Tests/TestHBIL/2018%20Mayaux%20-%20Horizon-Based%20Indirect%20Lighting%20(HBIL).pdf)
## Platform Support
* SSAO currently does not work on DirectX12 due to issues with wgpu and
naga:
* https://github.com/gfx-rs/wgpu/pull/3798
* https://github.com/gfx-rs/naga/pull/2353
* SSAO currently does not work on WebGPU because r16float is not a valid
storage texture format
https://gpuweb.github.io/gpuweb/wgsl/#storage-texel-formats. We can fix
this with a fallback to r32float.
---
## Changelog
- Added ScreenSpaceAmbientOcclusionSettings,
ScreenSpaceAmbientOcclusionQualityLevel, and
ScreenSpaceAmbientOcclusionBundle
---------
Co-authored-by: IceSentry <c.giguere42@gmail.com>
Co-authored-by: IceSentry <IceSentry@users.noreply.github.com>
Co-authored-by: Daniel Chia <danstryder@gmail.com>
Co-authored-by: Elabajaba <Elabajaba@users.noreply.github.com>
Co-authored-by: Robert Swain <robert.swain@gmail.com>
Co-authored-by: robtfm <50659922+robtfm@users.noreply.github.com>
Co-authored-by: Brandon Dyer <brandondyer64@gmail.com>
Co-authored-by: Edgar Geier <geieredgar@gmail.com>
Co-authored-by: Nicola Papale <nicopap@users.noreply.github.com>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
199 lines
6.1 KiB
Rust
199 lines
6.1 KiB
Rust
//! A scene showcasing screen space ambient occlusion.
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use bevy::{
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core_pipeline::experimental::taa::{TemporalAntiAliasBundle, TemporalAntiAliasPlugin},
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pbr::{
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ScreenSpaceAmbientOcclusionBundle, ScreenSpaceAmbientOcclusionQualityLevel,
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ScreenSpaceAmbientOcclusionSettings,
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},
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prelude::*,
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render::camera::TemporalJitter,
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};
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use std::f32::consts::PI;
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fn main() {
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App::new()
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.insert_resource(AmbientLight {
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brightness: 5.0,
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..default()
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})
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.add_plugins(DefaultPlugins)
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.add_plugin(TemporalAntiAliasPlugin)
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.add_systems(Startup, setup)
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.add_systems(Update, update)
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.run();
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}
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fn setup(
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mut commands: Commands,
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mut meshes: ResMut<Assets<Mesh>>,
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mut materials: ResMut<Assets<StandardMaterial>>,
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asset_server: Res<AssetServer>,
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) {
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commands
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.spawn(Camera3dBundle {
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camera: Camera {
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hdr: true,
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..default()
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},
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transform: Transform::from_xyz(-2.0, 2.0, -2.0).looking_at(Vec3::ZERO, Vec3::Y),
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..default()
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})
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.insert(ScreenSpaceAmbientOcclusionBundle::default())
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.insert(TemporalAntiAliasBundle::default());
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let material = materials.add(StandardMaterial {
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base_color: Color::rgb(0.5, 0.5, 0.5),
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perceptual_roughness: 1.0,
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reflectance: 0.0,
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..default()
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});
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commands.spawn(PbrBundle {
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mesh: meshes.add(Mesh::from(shape::Cube { size: 1.0 })),
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material: material.clone(),
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transform: Transform::from_xyz(0.0, 0.0, 1.0),
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..default()
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});
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commands.spawn(PbrBundle {
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mesh: meshes.add(Mesh::from(shape::Cube { size: 1.0 })),
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material: material.clone(),
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transform: Transform::from_xyz(0.0, -1.0, 0.0),
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..default()
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});
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commands.spawn(PbrBundle {
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mesh: meshes.add(Mesh::from(shape::Cube { size: 1.0 })),
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material,
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transform: Transform::from_xyz(1.0, 0.0, 0.0),
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..default()
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});
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commands.spawn((
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PbrBundle {
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mesh: meshes.add(Mesh::from(shape::UVSphere {
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radius: 0.4,
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sectors: 72,
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stacks: 36,
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})),
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material: materials.add(StandardMaterial {
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base_color: Color::rgb(0.4, 0.4, 0.4),
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perceptual_roughness: 1.0,
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reflectance: 0.0,
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..default()
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}),
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..default()
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},
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SphereMarker,
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));
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commands.spawn(DirectionalLightBundle {
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directional_light: DirectionalLight {
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shadows_enabled: true,
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..default()
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},
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transform: Transform::from_rotation(Quat::from_euler(
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EulerRot::ZYX,
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0.0,
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PI * -0.15,
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PI * -0.15,
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)),
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..default()
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});
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commands.spawn(
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TextBundle::from_section(
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"",
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TextStyle {
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font: asset_server.load("fonts/FiraMono-Medium.ttf"),
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font_size: 26.0,
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color: Color::BLACK,
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},
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)
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.with_style(Style {
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position_type: PositionType::Absolute,
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bottom: Val::Px(10.0),
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left: Val::Px(10.0),
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..default()
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}),
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);
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}
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fn update(
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camera: Query<
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(
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Entity,
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Option<&ScreenSpaceAmbientOcclusionSettings>,
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Option<&TemporalJitter>,
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),
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With<Camera>,
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>,
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mut text: Query<&mut Text>,
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mut sphere: Query<&mut Transform, With<SphereMarker>>,
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mut commands: Commands,
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keycode: Res<Input<KeyCode>>,
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time: Res<Time>,
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) {
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let mut sphere = sphere.single_mut();
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sphere.translation.y = (time.elapsed_seconds() / 1.7).sin() * 0.7;
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let (camera_entity, ssao_settings, temporal_jitter) = camera.single();
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let mut commands = commands.entity(camera_entity);
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if keycode.just_pressed(KeyCode::Key1) {
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commands.remove::<ScreenSpaceAmbientOcclusionSettings>();
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}
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if keycode.just_pressed(KeyCode::Key2) {
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commands.insert(ScreenSpaceAmbientOcclusionSettings {
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quality_level: ScreenSpaceAmbientOcclusionQualityLevel::Low,
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});
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}
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if keycode.just_pressed(KeyCode::Key3) {
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commands.insert(ScreenSpaceAmbientOcclusionSettings {
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quality_level: ScreenSpaceAmbientOcclusionQualityLevel::Medium,
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});
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}
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if keycode.just_pressed(KeyCode::Key4) {
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commands.insert(ScreenSpaceAmbientOcclusionSettings {
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quality_level: ScreenSpaceAmbientOcclusionQualityLevel::High,
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});
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}
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if keycode.just_pressed(KeyCode::Key5) {
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commands.insert(ScreenSpaceAmbientOcclusionSettings {
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quality_level: ScreenSpaceAmbientOcclusionQualityLevel::Ultra,
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});
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}
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if keycode.just_pressed(KeyCode::Space) {
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if temporal_jitter.is_some() {
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commands.remove::<TemporalJitter>();
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} else {
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commands.insert(TemporalJitter::default());
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}
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}
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let mut text = text.single_mut();
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let text = &mut text.sections[0].value;
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text.clear();
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let (o, l, m, h, u) = match ssao_settings.map(|s| s.quality_level) {
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None => ("*", "", "", "", ""),
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Some(ScreenSpaceAmbientOcclusionQualityLevel::Low) => ("", "*", "", "", ""),
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Some(ScreenSpaceAmbientOcclusionQualityLevel::Medium) => ("", "", "*", "", ""),
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Some(ScreenSpaceAmbientOcclusionQualityLevel::High) => ("", "", "", "*", ""),
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Some(ScreenSpaceAmbientOcclusionQualityLevel::Ultra) => ("", "", "", "", "*"),
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_ => unreachable!(),
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};
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text.push_str("SSAO Quality:\n");
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text.push_str(&format!("(1) {o}Off{o}\n"));
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text.push_str(&format!("(2) {l}Low{l}\n"));
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text.push_str(&format!("(3) {m}Medium{m}\n"));
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text.push_str(&format!("(4) {h}High{h}\n"));
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text.push_str(&format!("(5) {u}Ultra{u}\n\n"));
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text.push_str("Temporal Antialiasing:\n");
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text.push_str(match temporal_jitter {
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Some(_) => "(Space) Enabled",
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None => "(Space) Disabled",
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});
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}
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#[derive(Component)]
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struct SphereMarker;
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