wip

assets/shaders/custom_material.frag

@@ -0,0 +1,14 @@
+#version 450
+
+layout(location = 0) in vec2 v_uv;
+layout(location = 0) out vec4 o_color;
+
+layout(set = 0, binding = 0) uniform MaterialUniform {
+    vec4 color;
+} material;
+
+void main() {
+    // simple uv-based gradient multiplied by uniform color
+    vec3 grad = vec3(v_uv, 0.5);
+    o_color = material.color * vec4(grad, 1.0);
+}

assets/shaders/custom_material.vert

@@ -0,0 +1,12 @@
+#version 450
+
+// Minimal passthrough vertex shader for a fullscreen plane.
+layout(location = 0) in vec3 Vertex_Position;
+layout(location = 1) in vec2 Vertex_Uv;
+
+layout(location = 0) out vec2 v_uv;
+
+void main() {
+    v_uv = Vertex_Uv;
+    gl_Position = vec4(Vertex_Position, 1.0);
+}

src/main.rs

@@ -1,7 +1,9 @@
 //! A shader that uses the GLSL shading language.
 
 use bevy::{
-    prelude::*, reflect::TypePath, render::render_resource::AsBindGroup, render::render_resource::ShaderRef,
+    prelude::*,
+    reflect::TypePath,
+    render::render_resource::{AsBindGroup, ShaderRef},
 };
 
 /// This example uses shader source files from the assets subdirectory
@@ -10,34 +12,32 @@ const FRAGMENT_SHADER_ASSET_PATH: &str = "shaders/custom_material.frag";
 
 fn main() {
     App::new()
-        .add_plugins((DefaultPlugins, MaterialPlugin::<CustomMaterial>::default()))
+        .add_plugins(DefaultPlugins)
+        .add_plugins(MaterialPlugin::<CustomMaterial>::default())
         .add_systems(Startup, setup)
         .run();
 }
 
-/// set up a simple 3D scene
+/// set up a simple 2D-screen-like surface
 fn setup(
     mut commands: Commands,
     mut meshes: ResMut<Assets<Mesh>>,
     mut materials: ResMut<Assets<CustomMaterial>>,
-    asset_server: Res<AssetServer>,
 ) {
-    // cube
+    // Fullscreen flat surface: use a very large, thin cuboid so it behaves like a plane
     commands.spawn((
         Mesh3d(meshes.add(Cuboid::default())),
         MeshMaterial3d(materials.add(CustomMaterial {
-            color: LinearRgba::BLUE,
+            color: LinearRgba::new(0.2, 0.6, 0.9, 1.0),
             color_texture: None,
-            alpha_mode: AlphaMode::Blend,
+            alpha_mode: AlphaMode::Opaque,
         })),
-        Transform::from_xyz(0.0, 0.5, 0.0),
+        // Scale X/Y large to cover the camera view, keep Z very small to make it effectively a plane
+        Transform::from_scale(Vec3::new(2000.0, 2000.0, 0.01)),
     ));
 
-    // camera
-    commands.spawn((
-        Camera3d::default(),
-        Transform::from_xyz(-2.0, 2.5, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
-    ));
+    // 2D camera so the scene renders as a flat screen
+    commands.spawn((Camera2d::default(), Transform::default()));
 }
 
 // This is the struct that will be passed to your shader