use bevy::{     prelude::*, reflect::TypePath, render::render_resource::AsBindGroup, shader::ShaderRef, };  /// This example uses a shader source file from the assets subdirectory const SHADER_ASSET_PATH: &str = "shaders/custom_material_screenspace_texture.wgsl";  fn main() {     App::new()         .add_plugins((DefaultPlugins, MaterialPlugin::<CustomMaterial>::default()))         .add_systems(Startup, setup)         .add_systems(Update, rotate_camera)         .run(); }  #[derive(Component)] struct MainCamera;  fn setup(     mut commands: Commands,     asset_server: Res<AssetServer>,     mut meshes: ResMut<Assets<Mesh>>,     mut custom_materials: ResMut<Assets<CustomMaterial>>,     mut standard_materials: ResMut<Assets<StandardMaterial>>, ) {     commands.spawn((         Mesh3d(meshes.add(Plane3d::default().mesh().size(5.0, 5.0))),         MeshMaterial3d(standard_materials.add(Color::srgb(0.3, 0.5, 0.3))),     ));     commands.spawn((PointLight::default(), Transform::from_xyz(4.0, 8.0, 4.0)));      commands.spawn((         Mesh3d(meshes.add(Cuboid::default())),         MeshMaterial3d(custom_materials.add(CustomMaterial {             texture: asset_server.load(                 "models/FlightHelmet/FlightHelmet_Materials_LensesMat_OcclusionRoughMetal.png",             ),         })),         Transform::from_xyz(0.0, 0.5, 0.0),     ));      // camera     commands.spawn((         Camera3d::default(),         Transform::from_xyz(4.0, 2.5, 4.0).looking_at(Vec3::ZERO, Vec3::Y),         MainCamera,     )); }  fn rotate_camera(mut cam_transform: Single<&mut Transform, With<MainCamera>>, time: Res<Time>) {     cam_transform.rotate_around(         Vec3::ZERO,         Quat::from_axis_angle(Vec3::Y, 45f32.to_radians() * time.delta_secs()),     );     cam_transform.look_at(Vec3::ZERO, Vec3::Y); }  #[derive(Asset, TypePath, AsBindGroup, Debug, Clone)] struct CustomMaterial {     #[texture(0)]     #[sampler(1)]     texture: Handle<Image>, }  impl Material for CustomMaterial {     fn fragment_shader() -> ShaderRef {         SHADER_ASSET_PATH.into()     } } 

#import bevy_pbr::{     mesh_view_bindings::view,     forward_io::VertexOutput,     utils::coords_to_viewport_uv, }  @group(#{MATERIAL_BIND_GROUP}) @binding(0) var texture: texture_2d<f32>; @group(#{MATERIAL_BIND_GROUP}) @binding(1) var texture_sampler: sampler;  @fragment fn fragment(     mesh: VertexOutput, ) -> @location(0) vec4<f32> {     let viewport_uv = coords_to_viewport_uv(mesh.position.xy, view.viewport);     let color = textureSample(texture, texture_sampler, viewport_uv);     return color; }