Render groups example (bevyengine#2)

* RenderGroups example.

Cargo.toml

@@ -1993,6 +1993,17 @@ description = "Demonstrates loading from and saving scenes to files"
 category = "Scene"
 wasm = false
 
+[[example]]
+name = "render_groups"
+path = "examples/3d/render_groups.rs"
+doc-scrape-examples = true
+
+[package.metadata.example.render_groups]
+name = "Render Groups"
+description = "Spawning multiple copies of a scene from a GLTF file, each with a different render group"
+category = "3D Rendering"
+wasm = true
+
 # Shaders
 [[package.metadata.example_category]]
 name = "Shaders"

examples/3d/render_groups.rs

@@ -0,0 +1,131 @@
+//! Load a scene from a glTF file and render it with different render groups.
+
+use bevy::{
+    color::palettes,
+    pbr::DirectionalLightShadowMap,
+    prelude::*,
+    render::view::{CameraView, PropagateRenderGroups, RenderGroups},
+};
+
+fn main() {
+    App::new()
+        .insert_resource(DirectionalLightShadowMap { size: 4096 })
+        .add_plugins(DefaultPlugins)
+        .add_systems(Startup, setup)
+        .add_systems(Update, toggle_layers)
+        .run();
+}
+
+#[derive(Component)]
+struct MovedScene;
+
+fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
+    commands.spawn((
+        DirectionalLightBundle {
+            transform: Transform::from_xyz(4.0, 25.0, 8.0).looking_at(Vec3::ZERO, Vec3::Y),
+            directional_light: DirectionalLight {
+                shadows_enabled: true,
+                illuminance: 100000.0,
+                color: palettes::basic::RED.into(),
+                ..default()
+            },
+            ..default()
+        },
+        RenderGroups::from_layers(&[1, 2, 3]),
+    ));
+
+    commands.spawn((
+        Camera3dBundle {
+            transform: Transform::from_xyz(0., 1.4, 2.0)
+                .looking_at(Vec3::new(0., 0.3, 0.0), Vec3::Y),
+            ..default()
+        },
+        EnvironmentMapLight {
+            diffuse_map: asset_server.load("environment_maps/pisa_diffuse_rgb9e5_zstd.ktx2"),
+            specular_map: asset_server.load("environment_maps/pisa_specular_rgb9e5_zstd.ktx2"),
+            intensity: 1500.0,
+        },
+        CameraView::from_layers(&[0, 1, 2, 3]),
+    ));
+
+    commands.spawn((
+        TextBundle::from_section(
+            "Press '1..3' to toggle camera render layers\n\
+            Press '4..6' to toggle directional light render layers",
+            TextStyle {
+                font_size: 20.,
+                ..default()
+            },
+        )
+        .with_style(Style {
+            position_type: PositionType::Absolute,
+            top: Val::Px(12.0),
+            left: Val::Px(12.0),
+            ..default()
+        }),
+        RenderGroups::from_layer(0),
+    ));
+
+    // Spawn three copies of the scene, each with a different render group.
+    for i in 0..3 {
+        commands.spawn((
+            SceneBundle {
+                transform: Transform::from_xyz(i as f32 - 1.0, 0.0, 0.0),
+                scene: asset_server.load("models/FlightHelmet/FlightHelmet.gltf#Scene0"),
+                ..default()
+            },
+            RenderGroups::from_layer(i + 1),
+            PropagateRenderGroups::Auto,
+        ));
+    }
+}
+
+fn toggle_layers(
+    mut query_camera: Query<&mut CameraView>,
+    mut query_light: Query<&mut RenderGroups, With<DirectionalLight>>,
+    keyboard: Res<ButtonInput<KeyCode>>,
+) {
+    let Ok(mut camera_view) = query_camera.get_single_mut() else {
+        return;
+    };
+
+    let Ok(mut light_groups) = query_light.get_single_mut() else {
+        return;
+    };
+
+    if keyboard.just_pressed(KeyCode::Digit1) {
+        toggle_camera_layer(&mut camera_view, 1);
+    }
+    if keyboard.just_pressed(KeyCode::Digit2) {
+        toggle_camera_layer(&mut camera_view, 2);
+    }
+    if keyboard.just_pressed(KeyCode::Digit3) {
+        toggle_camera_layer(&mut camera_view, 3);
+    }
+
+    if keyboard.just_pressed(KeyCode::Digit4) {
+        toggle_render_layer(&mut light_groups, 1);
+    }
+    if keyboard.just_pressed(KeyCode::Digit5) {
+        toggle_render_layer(&mut light_groups, 2);
+    }
+    if keyboard.just_pressed(KeyCode::Digit6) {
+        toggle_render_layer(&mut light_groups, 3);
+    }
+}
+
+fn toggle_camera_layer(camera_view: &mut CameraView, layer: usize) {
+    if camera_view.contains_layer(layer) {
+        camera_view.remove(layer);
+    } else {
+        camera_view.add(layer);
+    }
+}
+
+fn toggle_render_layer(groups: &mut RenderGroups, layer: usize) {
+    if groups.contains_layer(layer) {
+        groups.remove(layer);
+    } else {
+        groups.add(layer);
+    }
+}