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add a post-processing example (#4797)
# Objective - Add an example showing a custom post processing effect, done after the first rendering pass. ## Solution - A simple post processing "chromatic aberration" effect. I mixed together examples `3d/render_to_texture`, and `shader/shader_material_screenspace_texture` - Reading a bit how https://github.com/bevyengine/bevy/pull/3430 was done gave me pointers to apply the main pass to the 2d render rather than using a 3d quad. This work might be or not be relevant to https://github.com/bevyengine/bevy/issues/2724 <details> <summary> ⚠️ Click for a video of the render ⚠️ I’ve been told it might hurt the eyes 👀 , maybe we should choose another effect just in case ?</summary> https://user-images.githubusercontent.com/2290685/169138830-a6dc8a9f-8798-44b9-8d9e-449e60614916.mp4 </details> # Request for feedbacks - [ ] Is chromatic aberration effect ok ? (Correct term, not a danger for the eyes ?) I'm open to suggestion to make something different. - [ ] Is the code idiomatic ? I preferred a "main camera -> **new camera with post processing applied to a quad**" approach to emulate minimum modification to existing code wanting to add global post processing. --- ## Changelog - Add a full screen post processing shader example
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@ -512,6 +512,10 @@ path = "examples/scene/scene.rs"
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name = "custom_vertex_attribute"
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path = "examples/shader/custom_vertex_attribute.rs"
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[[example]]
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name = "post_processing"
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path = "examples/shader/post_processing.rs"
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[[example]]
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name = "shader_defs"
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path = "examples/shader/shader_defs.rs"
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25
assets/shaders/custom_material_chromatic_aberration.wgsl
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25
assets/shaders/custom_material_chromatic_aberration.wgsl
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@ -0,0 +1,25 @@
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#import bevy_pbr::mesh_view_bindings
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[[group(1), binding(0)]]
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var texture: texture_2d<f32>;
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[[group(1), binding(1)]]
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var our_sampler: sampler;
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[[stage(fragment)]]
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fn fragment([[builtin(position)]] position: vec4<f32>) -> [[location(0)]] vec4<f32> {
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// Get screen position with coordinates from 0 to 1
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let uv = position.xy / vec2<f32>(view.width, view.height);
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let offset_strength = 0.02;
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// Sample each color channel with an arbitrary shift
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var output_color = vec4<f32>(
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textureSample(texture, our_sampler, uv + vec2<f32>(offset_strength, -offset_strength)).r,
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textureSample(texture, our_sampler, uv + vec2<f32>(-offset_strength, 0.0)).g,
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textureSample(texture, our_sampler, uv + vec2<f32>(0.0, offset_strength)).b,
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1.0
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);
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return output_color;
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}
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@ -253,6 +253,7 @@ Example | File | Description
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`animate_shader` | [`shader/animate_shader.rs`](./shader/animate_shader.rs) | A shader that uses dynamic data like the time since startup.
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`compute_shader_game_of_life` | [`shader/compute_shader_game_of_life.rs`](./shader/compute_shader_game_of_life.rs) | A compute shader that simulates Conway's Game of Life.
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`custom_vertex_attribute` | [`shader/custom_vertex_attribute.rs`](./shader/custom_vertex_attribute.rs) | A shader that reads a mesh's custom vertex attribute.
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`post_processing` | [`shader/post_processing.rs`](./shader/post_processing.rs) | A custom post processing effect, using two cameras, with one reusing the render texture of the first one.
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`shader_defs` | [`shader/shader_defs.rs`](./shader/shader_defs.rs) | A shader that uses "shaders defs" (a bevy tool to selectively toggle parts of a shader).
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`shader_instancing` | [`shader/shader_instancing.rs`](./shader/shader_instancing.rs) | A shader that renders a mesh multiple times in one draw call.
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`shader_material` | [`shader/shader_material.rs`](./shader/shader_material.rs) | A shader and a material that uses it.
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256
examples/shader/post_processing.rs
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examples/shader/post_processing.rs
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//! A custom post processing effect, using two cameras, with one reusing the render texture of the first one.
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//! Here a chromatic aberration is applied to a 3d scene containting a rotating cube.
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//! This example is useful to implement your own post-processing effect such as
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//! edge detection, blur, pixelization, vignette... and countless others.
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use bevy::{
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core_pipeline::clear_color::ClearColorConfig,
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ecs::system::{lifetimeless::SRes, SystemParamItem},
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prelude::*,
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reflect::TypeUuid,
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render::{
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camera::{Camera, RenderTarget},
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render_asset::{PrepareAssetError, RenderAsset, RenderAssets},
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render_resource::{
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BindGroup, BindGroupDescriptor, BindGroupEntry, BindGroupLayout,
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BindGroupLayoutDescriptor, BindGroupLayoutEntry, BindingResource, BindingType,
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Extent3d, SamplerBindingType, ShaderStages, TextureDescriptor, TextureDimension,
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TextureFormat, TextureSampleType, TextureUsages, TextureViewDimension,
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},
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renderer::RenderDevice,
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view::RenderLayers,
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},
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sprite::{Material2d, Material2dPipeline, Material2dPlugin, MaterialMesh2dBundle},
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};
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fn main() {
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let mut app = App::new();
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app.add_plugins(DefaultPlugins)
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.add_plugin(Material2dPlugin::<PostProcessingMaterial>::default())
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.add_startup_system(setup)
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.add_system(main_camera_cube_rotator_system);
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app.run();
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}
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/// Marks the first camera cube (rendered to a texture.)
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#[derive(Component)]
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struct MainCube;
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fn setup(
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mut commands: Commands,
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mut windows: ResMut<Windows>,
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mut meshes: ResMut<Assets<Mesh>>,
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mut post_processing_materials: ResMut<Assets<PostProcessingMaterial>>,
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mut materials: ResMut<Assets<StandardMaterial>>,
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mut images: ResMut<Assets<Image>>,
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) {
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let window = windows.get_primary_mut().unwrap();
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let size = Extent3d {
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width: window.physical_width(),
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height: window.physical_height(),
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..default()
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};
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// This is the texture that will be rendered to.
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let mut image = Image {
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texture_descriptor: TextureDescriptor {
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label: None,
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size,
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dimension: TextureDimension::D2,
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format: TextureFormat::Bgra8UnormSrgb,
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mip_level_count: 1,
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sample_count: 1,
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usage: TextureUsages::TEXTURE_BINDING
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| TextureUsages::COPY_DST
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| TextureUsages::RENDER_ATTACHMENT,
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},
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..default()
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};
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// fill image.data with zeroes
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image.resize(size);
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let image_handle = images.add(image);
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let cube_handle = meshes.add(Mesh::from(shape::Cube { size: 4.0 }));
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let cube_material_handle = materials.add(StandardMaterial {
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base_color: Color::rgb(0.8, 0.7, 0.6),
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reflectance: 0.02,
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unlit: false,
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..default()
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});
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// The cube that will be rendered to the texture.
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commands
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.spawn_bundle(PbrBundle {
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mesh: cube_handle,
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material: cube_material_handle,
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transform: Transform::from_translation(Vec3::new(0.0, 0.0, 1.0)),
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..default()
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})
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.insert(MainCube);
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// Light
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// NOTE: Currently lights are ignoring render layers - see https://github.com/bevyengine/bevy/issues/3462
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commands.spawn_bundle(PointLightBundle {
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transform: Transform::from_translation(Vec3::new(0.0, 0.0, 10.0)),
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..default()
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});
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// Main camera, first to render
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commands.spawn_bundle(Camera3dBundle {
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camera_3d: Camera3d {
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clear_color: ClearColorConfig::Custom(Color::WHITE),
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},
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camera: Camera {
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target: RenderTarget::Image(image_handle.clone()),
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..default()
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},
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transform: Transform::from_translation(Vec3::new(0.0, 0.0, 15.0))
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.looking_at(Vec3::default(), Vec3::Y),
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..default()
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});
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// This specifies the layer used for the post processing camera, which will be attached to the post processing camera and 2d quad.
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let post_processing_pass_layer = RenderLayers::layer((RenderLayers::TOTAL_LAYERS - 1) as u8);
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let quad_handle = meshes.add(Mesh::from(shape::Quad::new(Vec2::new(
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size.width as f32,
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size.height as f32,
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))));
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// This material has the texture that has been rendered.
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let material_handle = post_processing_materials.add(PostProcessingMaterial {
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source_image: image_handle,
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});
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// Post processing 2d quad, with material using the render texture done by the main camera, with a custom shader.
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commands
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.spawn_bundle(MaterialMesh2dBundle {
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mesh: quad_handle.into(),
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material: material_handle,
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transform: Transform {
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translation: Vec3::new(0.0, 0.0, 1.5),
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..default()
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},
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..default()
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})
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.insert(post_processing_pass_layer);
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// The post-processing pass camera.
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commands
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.spawn_bundle(Camera2dBundle {
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camera: Camera {
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// renders after the first main camera which has default value: 0.
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priority: 1,
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..default()
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},
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..Camera2dBundle::default()
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})
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.insert(post_processing_pass_layer);
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}
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/// Rotates the cube rendered by the main camera
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fn main_camera_cube_rotator_system(
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time: Res<Time>,
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mut query: Query<&mut Transform, With<MainCube>>,
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) {
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for mut transform in query.iter_mut() {
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transform.rotation *= Quat::from_rotation_x(0.55 * time.delta_seconds());
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transform.rotation *= Quat::from_rotation_z(0.15 * time.delta_seconds());
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}
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}
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// Region below declares of the custom material handling post processing effect
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/// Our custom post processing material
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#[derive(TypeUuid, Clone)]
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#[uuid = "bc2f08eb-a0fb-43f1-a908-54871ea597d5"]
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struct PostProcessingMaterial {
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/// In this example, this image will be the result of the main camera.
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source_image: Handle<Image>,
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}
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struct PostProcessingMaterialGPU {
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bind_group: BindGroup,
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}
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impl Material2d for PostProcessingMaterial {
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fn bind_group(material: &PostProcessingMaterialGPU) -> &BindGroup {
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&material.bind_group
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}
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fn bind_group_layout(render_device: &RenderDevice) -> BindGroupLayout {
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render_device.create_bind_group_layout(&BindGroupLayoutDescriptor {
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label: None,
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entries: &[
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BindGroupLayoutEntry {
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binding: 0,
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visibility: ShaderStages::FRAGMENT,
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ty: BindingType::Texture {
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multisampled: false,
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view_dimension: TextureViewDimension::D2,
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sample_type: TextureSampleType::Float { filterable: true },
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},
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count: None,
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},
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BindGroupLayoutEntry {
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binding: 1,
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visibility: ShaderStages::FRAGMENT,
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ty: BindingType::Sampler(SamplerBindingType::Filtering),
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count: None,
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},
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],
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})
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}
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fn fragment_shader(asset_server: &AssetServer) -> Option<Handle<Shader>> {
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asset_server.watch_for_changes().unwrap();
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Some(asset_server.load("shaders/custom_material_chromatic_aberration.wgsl"))
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}
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}
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impl RenderAsset for PostProcessingMaterial {
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type ExtractedAsset = PostProcessingMaterial;
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type PreparedAsset = PostProcessingMaterialGPU;
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type Param = (
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SRes<RenderDevice>,
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SRes<Material2dPipeline<PostProcessingMaterial>>,
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SRes<RenderAssets<Image>>,
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);
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fn prepare_asset(
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extracted_asset: PostProcessingMaterial,
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(render_device, pipeline, images): &mut SystemParamItem<Self::Param>,
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) -> Result<PostProcessingMaterialGPU, PrepareAssetError<PostProcessingMaterial>> {
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let (view, sampler) = if let Some(result) = pipeline
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.mesh2d_pipeline
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.get_image_texture(images, &Some(extracted_asset.source_image.clone()))
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{
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result
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} else {
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return Err(PrepareAssetError::RetryNextUpdate(extracted_asset));
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};
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let bind_group = render_device.create_bind_group(&BindGroupDescriptor {
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label: None,
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layout: &pipeline.material2d_layout,
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entries: &[
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BindGroupEntry {
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binding: 0,
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resource: BindingResource::TextureView(view),
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},
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BindGroupEntry {
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binding: 1,
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resource: BindingResource::Sampler(sampler),
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},
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],
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});
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Ok(PostProcessingMaterialGPU { bind_group })
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}
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fn extract_asset(&self) -> PostProcessingMaterial {
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self.clone()
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}
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}
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