wip

assets/shaders/default.wgsl

@@ -1,30 +1,18 @@
-// Simple UV gradient shader (vertex + fragment)
+#import bevy_sprite::mesh2d_vertex_output::VertexOutput
 
-struct VertexInput {
-    @location(0) position: vec3<f32>,
-    @location(1) uv: vec2<f32>,
-}
-
-struct VertexOutput {
-    @builtin(position) clip_position: vec4<f32>,
-    @location(0) uv: vec2<f32>,
-}
-
-@vertex
-fn vertex(in: VertexInput) -> VertexOutput {
-    var out: VertexOutput;
-    // assume incoming positions are in clip-space (vec3 with z, or model-transformed)
-    out.clip_position = vec4<f32>(in.position, 1.0);
-    out.uv = in.uv;
-    return out;
-}
+@group(2) @binding(0) var<uniform> u_time: f32;
+@group(2) @binding(1) var<uniform> u_resolution: vec2<f32>;
 
 @fragment
-fn fragment(in: VertexOutput) -> @location(0) vec4<f32> {
+fn fragment(mesh: VertexOutput) -> @location(0) vec4<f32> {
     // very simple vertical gradient between two colors
     let bottom = vec3<f32>(1.0, 0.8, 0.2); // warm
     let top    = vec3<f32>(0.2, 0.6, 1.0); // cool
 
-    let color = mix(bottom, top, in.uv.y);
+    // use time to subtly shift the gradient
+    let t = u_time;
+    let shift = 0.2 * sin(t);
+
+    let color = mix(bottom, top, mesh.uv.y + shift);
     return vec4<f32>(color, 1.0);
 }

src/main.rs

@@ -21,6 +21,7 @@ fn main() {
         .add_systems(
             Update,
             (
+                update_material_time,
                 resize_fullscreen_quad,
                 exit_app.run_if(input_just_pressed(KeyCode::Escape)),
                 toggle_fullscreen.run_if(input_just_pressed(KeyCode::F11)),
@@ -31,24 +32,30 @@ fn main() {
 
 /// set up a simple 2D-screen-like surface
 fn setup(
-    mut commands: Commands,
     mut meshes: ResMut<Assets<Mesh>>,
     mut materials: ResMut<Assets<CustomMaterial>>,
     mut primary_window: Single<&mut Window, With<PrimaryWindow>>,
+    mut commands: Commands,
 ) {
     primary_window.decorations = false;
 
     commands.spawn(Camera2d);
 
     // quad that fills the whole window
-    let size = Vec2::new(
+    let screen_size = Vec2::new(
         primary_window.resolution.width(),
         primary_window.resolution.height(),
     );
+    // create material with initial time = 0.0
+    let material_handle = materials.add(CustomMaterial {
+        time: 0.0,
+        resolution: screen_size,
+    });
+
     commands.spawn((
         Mesh2d(meshes.add(Rectangle::default())),
-        MeshMaterial2d(materials.add(CustomMaterial {})),
-        Transform::from_scale(Vec3::new(size.x, size.y, 1.0)),
+        MeshMaterial2d(material_handle),
+        Transform::from_scale(Vec3::new(screen_size.x, screen_size.y, 1.0)),
         FullscreenQuad,
     ));
 }
@@ -83,7 +90,19 @@ fn toggle_fullscreen(mut primary_window: Single<&mut Window, With<PrimaryWindow>
 
 // This is the struct that will be passed to your shader
 #[derive(Asset, TypePath, AsBindGroup, Clone)]
-struct CustomMaterial {}
+struct CustomMaterial {
+    #[uniform(0)]
+    time: f32,
+    #[uniform(1)]
+    resolution: Vec2,
+}
+
+fn update_material_time(mut materials: ResMut<Assets<CustomMaterial>>, time: Res<Time>) {
+    let t = time.elapsed_secs();
+    for (_handle, material) in materials.iter_mut() {
+        material.time = t;
+    }
+}
 
 /// The Material2d trait is very configurable, but comes with sensible defaults for all methods.
 /// You only need to implement functions for features that need non-default behavior. See the Material2d api docs for details!