feat: full-screen quad + BlackHoleMaterial pipeline

assets/shaders/black_hole.wgsl

@@ -0,0 +1,11 @@
+#import bevy_sprite::mesh2d_vertex_output::VertexOutput
+
+@group(#{MATERIAL_BIND_GROUP}) @binding(0) var<uniform> time: f32;
+
+@fragment
+fn fragment(in: VertexOutput) -> @location(0) vec4<f32> {
+    // Gradient from time, just to prove the uniform flows.
+    let t = (sin(time) + 1.0) * 0.5;
+    let col = mix(vec3<f32>(0.02, 0.02, 0.05), vec3<f32>(0.08, 0.04, 0.12), t);
+    return vec4<f32>(col, 1.0);
+}

src/main.rs

@@ -3,6 +3,7 @@ use bevy::window::WindowPlugin;
 
 #[cfg(target_arch = "wasm32")]
 mod web;
+mod render;
 
 fn main() {
     // On web, abort startup if WebGPU isn't available and show a message.
@@ -24,10 +25,6 @@ fn main() {
             }),
             ..default()
         }))
-        .add_systems(Startup, setup)
+        .add_plugins(render::BlackHolePlugin)
         .run();
 }
-
-fn setup(mut commands: Commands) {
-    commands.spawn(Camera2d);
-}

src/render/material.rs

@@ -0,0 +1,17 @@
+use bevy::prelude::*;
+use bevy::reflect::TypePath;
+use bevy::render::render_resource::AsBindGroup;
+use bevy::shader::ShaderRef;
+use bevy::sprite_render::Material2d;
+
+#[derive(Asset, TypePath, AsBindGroup, Debug, Clone)]
+pub struct BlackHoleMaterial {
+    #[uniform(0)]
+    pub time: f32,
+}
+
+impl Material2d for BlackHoleMaterial {
+    fn fragment_shader() -> ShaderRef {
+        "shaders/black_hole.wgsl".into()
+    }
+}

src/render/mod.rs

@@ -0,0 +1,4 @@
+pub mod plugin;
+pub mod material;
+
+pub use plugin::BlackHolePlugin;

src/render/plugin.rs

@@ -0,0 +1,33 @@
+use bevy::prelude::*;
+use bevy::sprite_render::Material2dPlugin;
+
+use super::material::BlackHoleMaterial;
+
+pub struct BlackHolePlugin;
+
+impl Plugin for BlackHolePlugin {
+    fn build(&self, app: &mut App) {
+        app.add_plugins(Material2dPlugin::<BlackHoleMaterial>::default())
+            .add_systems(Startup, spawn_fullscreen_quad)
+            .add_systems(Update, update_time);
+    }
+}
+
+fn spawn_fullscreen_quad(
+    mut commands: Commands,
+    mut meshes: ResMut<Assets<Mesh>>,
+    mut materials: ResMut<Assets<BlackHoleMaterial>>,
+) {
+    commands.spawn(Camera2d);
+    commands.spawn((
+        Mesh2d(meshes.add(Rectangle::new(2.0, 2.0))),
+        MeshMaterial2d(materials.add(BlackHoleMaterial { time: 0.0 })),
+        Transform::default(),
+    ));
+}
+
+fn update_time(time: Res<Time>, mut materials: ResMut<Assets<BlackHoleMaterial>>) {
+    for (_, mat) in materials.iter_mut() {
+        mat.time = time.elapsed_secs();
+    }
+}