add handling of all missing gltf extras: scene, mesh & materials (#13453)

# Objective

- fixes #4823 

## Solution

As outlined in the discussion in the linked issue as the best current
solution, this PR adds specific GltfExtras for
 - scenes 
 - meshes
 - materials

- As it is , it is not a breaking change, I hesitated to rename the
current "GltfExtras" component to "PrimitiveGltfExtras", but that would
result in a breaking change and might be a bit confusing as to what
"primitive" that refers to.
 

## Testing

- I included a bare-bones example & asset (exported gltf file from
Blender) with gltf extras at all the relevant levels : scene, mesh,
material

---

## Changelog
- adds "SceneGltfExtras" injected at the scene level if any
- adds "MeshGltfExtras", injected at the mesh level if any
- adds "MaterialGltfExtras", injected at the mesh level if any: ie if a
mesh has a material that has gltf extras, the component will be injected
there.

Cargo.toml

@@ -802,6 +802,17 @@ description = "Loads and renders a glTF file as a scene"
 category = "3D Rendering"
 wasm = true
 
+[[example]]
+name = "load_gltf_extras"
+path = "examples/3d/load_gltf_extras.rs"
+doc-scrape-examples = true
+
+[package.metadata.example.load_gltf_extras]
+name = "Load glTF extras"
+description = "Loads and renders a glTF file as a scene, including the gltf extras"
+category = "3D Rendering"
+wasm = true
+
 [[example]]
 name = "motion_blur"
 path = "examples/3d/motion_blur.rs"

crates/bevy_gltf/src/lib.rs

@@ -146,6 +146,9 @@ impl GltfPlugin {
 impl Plugin for GltfPlugin {
     fn build(&self, app: &mut App) {
         app.register_type::<GltfExtras>()
+            .register_type::<GltfSceneExtras>()
+            .register_type::<GltfMeshExtras>()
+            .register_type::<GltfMaterialExtras>()
             .init_asset::<Gltf>()
             .init_asset::<GltfNode>()
             .init_asset::<GltfPrimitive>()
@@ -239,7 +242,7 @@ pub struct GltfPrimitive {
     pub material_extras: Option<GltfExtras>,
 }
 
-/// Additional untyped data that can be present on most glTF types.
+/// Additional untyped data that can be present on most glTF types at the primitive level.
 ///
 /// See [the relevant glTF specification section](https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#reference-extras).
 #[derive(Clone, Debug, Reflect, Default, Component)]
@@ -249,6 +252,36 @@ pub struct GltfExtras {
     pub value: String,
 }
 
+/// Additional untyped data that can be present on most glTF types at the scene level.
+///
+/// See [the relevant glTF specification section](https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#reference-extras).
+#[derive(Clone, Debug, Reflect, Default, Component)]
+#[reflect(Component)]
+pub struct GltfSceneExtras {
+    /// Content of the extra data.
+    pub value: String,
+}
+
+/// Additional untyped data that can be present on most glTF types at the mesh level.
+///
+/// See [the relevant glTF specification section](https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#reference-extras).
+#[derive(Clone, Debug, Reflect, Default, Component)]
+#[reflect(Component)]
+pub struct GltfMeshExtras {
+    /// Content of the extra data.
+    pub value: String,
+}
+
+/// Additional untyped data that can be present on most glTF types at the material level.
+///
+/// See [the relevant glTF specification section](https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#reference-extras).
+#[derive(Clone, Debug, Reflect, Default, Component)]
+#[reflect(Component)]
+pub struct GltfMaterialExtras {
+    /// Content of the extra data.
+    pub value: String,
+}
+
 /// Labels that can be used to load part of a glTF
 ///
 /// You can use [`GltfAssetLabel::from_asset`] to add it to an asset path

crates/bevy_gltf/src/loader.rs

@@ -1,5 +1,8 @@
-use crate::GltfAssetLabel;
-use crate::{vertex_attributes::convert_attribute, Gltf, GltfExtras, GltfNode};
+use crate::{
+    vertex_attributes::convert_attribute, Gltf, GltfAssetLabel, GltfExtras, GltfMaterialExtras,
+    GltfMeshExtras, GltfNode, GltfSceneExtras,
+};
+
 #[cfg(feature = "bevy_animation")]
 use bevy_animation::{AnimationTarget, AnimationTargetId};
 use bevy_asset::{
@@ -634,7 +637,8 @@ async fn load_gltf<'a, 'b, 'c>(
         let mut node_index_to_entity_map = HashMap::new();
         let mut entity_to_skin_index_map = EntityHashMap::default();
         let mut scene_load_context = load_context.begin_labeled_asset();
-        world
+
+        let world_root_id = world
             .spawn(SpatialBundle::INHERITED_IDENTITY)
             .with_children(|parent| {
                 for node in scene.nodes() {
@@ -659,7 +663,15 @@ async fn load_gltf<'a, 'b, 'c>(
                         return;
                     }
                 }
+            })
+            .id();
+
+        if let Some(extras) = scene.extras().as_ref() {
+            world.entity_mut(world_root_id).insert(GltfSceneExtras {
+                value: extras.get().to_string(),
             });
+        }
+
         if let Some(Err(err)) = err {
             return Err(err);
         }
@@ -1270,6 +1282,7 @@ fn load_node(
                         material: load_context.get_label_handle(&material_label),
                         ..Default::default()
                     });
+
                     let target_count = primitive.morph_targets().len();
                     if target_count != 0 {
                         let weights = match mesh.weights() {
@@ -1300,6 +1313,18 @@ fn load_node(
                         });
                     }
 
+                    if let Some(extras) = mesh.extras() {
+                        mesh_entity.insert(GltfMeshExtras {
+                            value: extras.get().to_string(),
+                        });
+                    }
+
+                    if let Some(extras) = material.extras() {
+                        mesh_entity.insert(GltfMaterialExtras {
+                            value: extras.get().to_string(),
+                        });
+                    }
+
                     mesh_entity.insert(Name::new(primitive_name(&mesh, &primitive)));
                     // Mark for adding skinned mesh
                     if let Some(skin) = gltf_node.skin() {

examples/3d/load_gltf_extras.rs

@@ -0,0 +1,97 @@
+//! Loads and renders a glTF file as a scene, and list all the different `gltf_extras`.
+
+use bevy::{
+    gltf::{GltfExtras, GltfMaterialExtras, GltfMeshExtras, GltfSceneExtras},
+    prelude::*,
+};
+
+fn main() {
+    App::new()
+        .add_plugins(DefaultPlugins)
+        .add_systems(Startup, setup)
+        .add_systems(Update, check_for_gltf_extras)
+        .run();
+}
+
+#[derive(Component)]
+struct ExampleDisplay;
+
+fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
+    commands.spawn(Camera3dBundle {
+        transform: Transform::from_xyz(2.0, 2.0, 2.0).looking_at(Vec3::ZERO, Vec3::Y),
+        ..default()
+    });
+
+    commands.spawn(DirectionalLightBundle {
+        directional_light: DirectionalLight {
+            shadows_enabled: true,
+            ..default()
+        },
+        ..default()
+    });
+    // a barebones scene containing one of each gltf_extra type
+    commands.spawn(SceneBundle {
+        scene: asset_server.load("models/extras/gltf_extras.glb#Scene0"),
+        ..default()
+    });
+
+    // a place to display the extras on screen
+    commands.spawn((
+        TextBundle::from_section(
+            "",
+            TextStyle {
+                font_size: 18.,
+                ..default()
+            },
+        )
+        .with_style(Style {
+            position_type: PositionType::Absolute,
+            top: Val::Px(12.0),
+            left: Val::Px(12.0),
+            ..default()
+        }),
+        ExampleDisplay,
+    ));
+}
+
+fn check_for_gltf_extras(
+    gltf_extras_per_entity: Query<(
+        Entity,
+        Option<&Name>,
+        Option<&GltfSceneExtras>,
+        Option<&GltfExtras>,
+        Option<&GltfMeshExtras>,
+        Option<&GltfMaterialExtras>,
+    )>,
+    mut display: Query<&mut Text, With<ExampleDisplay>>,
+) {
+    let mut gltf_extra_infos_lines: Vec<String> = vec![];
+
+    for (id, name, scene_extras, extras, mesh_extras, material_extras) in
+        gltf_extras_per_entity.iter()
+    {
+        if scene_extras.is_some()
+            || extras.is_some()
+            || mesh_extras.is_some()
+            || material_extras.is_some()
+        {
+            let formatted_extras = format!(
+                "Extras per entity {} ('Name: {}'):
+    - scene extras:     {:?}
+    - primitive extras: {:?}
+    - mesh extras:      {:?}
+    - material extras:  {:?}
+                ",
+                id,
+                name.unwrap_or(&Name::default()),
+                scene_extras,
+                extras,
+                mesh_extras,
+                material_extras
+            );
+            gltf_extra_infos_lines.push(formatted_extras);
+        }
+        let mut display = display.single_mut();
+        display.sections[0].value = gltf_extra_infos_lines.join("\n");
+    }
+}

examples/README.md

@@ -143,6 +143,7 @@ Example | Description
 [Lightmaps](../examples/3d/lightmaps.rs) | Rendering a scene with baked lightmaps
 [Lines](../examples/3d/lines.rs) | Create a custom material to draw 3d lines
 [Load glTF](../examples/3d/load_gltf.rs) | Loads and renders a glTF file as a scene
+[Load glTF extras](../examples/3d/load_gltf_extras.rs) | Loads and renders a glTF file as a scene, including the gltf extras
 [Meshlet](../examples/3d/meshlet.rs) | Meshlet rendering for dense high-poly scenes (experimental)
 [Motion Blur](../examples/3d/motion_blur.rs) | Demonstrates per-pixel motion blur
 [Orthographic View](../examples/3d/orthographic.rs) | Shows how to create a 3D orthographic view (for isometric-look in games or CAD applications)