gltf_extension_mesh_2d/
gltf_extension_mesh_2d.rs

1//! Uses glTF extension processing to convert incoming 3d Meshes to 2d Meshes
2
3use bevy::{
4    asset::LoadContext,
5    gltf::{
6        extensions::{ErasedGltfExtensionHandler, GltfExtensionHandler, GltfExtensionHandlers},
7        GltfPlugin,
8    },
9    mesh::{MeshVertexAttribute, MeshVertexBufferLayoutRef},
10    pbr::PbrPlugin,
11    prelude::*,
12    reflect::TypePath,
13    render::render_resource::*,
14    shader::ShaderRef,
15    sprite_render::{Material2d, Material2dKey, Material2dPlugin},
16};
17
18/// This example uses a shader source file from the assets subdirectory
19const SHADER_ASSET_PATH: &str = "shaders/custom_gltf_2d.wgsl";
20
21/// This vertex attribute supplies barycentric coordinates for each triangle.
22///
23/// Each component of the vector corresponds to one corner of a triangle. It's
24/// equal to 1.0 in that corner and 0.0 in the other two. Hence, its value in
25/// the fragment shader indicates proximity to a corner or the opposite edge.
26const ATTRIBUTE_BARYCENTRIC: MeshVertexAttribute =
27    MeshVertexAttribute::new("Barycentric", 2137464976, VertexFormat::Float32x3);
28
29fn main() {
30    App::new()
31        .insert_resource(GlobalAmbientLight {
32            color: Color::WHITE,
33            brightness: 2000.,
34            ..default()
35        })
36        .add_plugins((
37            DefaultPlugins
38                .set(
39                    GltfPlugin::default()
40                        // Map a custom glTF attribute name to a `MeshVertexAttribute`.
41                        // The glTF file used here has an attribute name with *two*
42                        // underscores: __BARYCENTRIC
43                        // One is stripped to do the comparison here.
44                        .add_custom_vertex_attribute("_BARYCENTRIC", ATTRIBUTE_BARYCENTRIC),
45                )
46                .set(PbrPlugin {
47                    gltf_enable_standard_materials: false,
48                    ..Default::default()
49                }),
50            GltfToMesh2dPlugin,
51        ))
52        .add_systems(Startup, setup)
53        .run();
54}
55
56fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
57    commands.spawn((
58        WorldAssetRoot(
59            asset_server
60                .load(GltfAssetLabel::Scene(0).from_asset("models/barycentric/barycentric.gltf")),
61        ),
62        Transform::from_scale(150. * Vec3::ONE),
63    ));
64    commands.spawn(Camera2d);
65}
66
67struct GltfToMesh2dPlugin;
68
69impl Plugin for GltfToMesh2dPlugin {
70    fn build(&self, app: &mut App) {
71        #[cfg(target_family = "wasm")]
72        bevy::tasks::block_on(async {
73            app.world_mut()
74                .resource_mut::<GltfExtensionHandlers>()
75                .0
76                .write()
77                .await
78                .push(Box::new(GltfExtensionHandlerToMesh2d))
79        });
80        #[cfg(not(target_family = "wasm"))]
81        app.world_mut()
82            .resource_mut::<GltfExtensionHandlers>()
83            .0
84            .write_blocking()
85            .push(Box::new(GltfExtensionHandlerToMesh2d));
86
87        app.add_plugins(Material2dPlugin::<CustomMaterial>::default());
88    }
89}
90
91#[derive(Default, Clone)]
92struct GltfExtensionHandlerToMesh2d;
93
94impl GltfExtensionHandler for GltfExtensionHandlerToMesh2d {
95    fn dyn_clone(&self) -> Box<dyn ErasedGltfExtensionHandler> {
96        Box::new((*self).clone())
97    }
98
99    fn on_spawn_mesh_and_material(
100        &mut self,
101        load_context: &mut LoadContext<'_>,
102        _primitive: &gltf::Primitive,
103        _mesh: &gltf::Mesh,
104        _material: &gltf::Material,
105        entity: &mut EntityWorldMut,
106        _material_label: &str,
107    ) {
108        if let Some(mesh3d) = entity.get::<Mesh3d>() {
109            let material_handle =
110                load_context.add_labeled_asset("AColorMaterial".to_string(), CustomMaterial {});
111            let mesh_handle = mesh3d.0.clone();
112            entity
113                .remove::<Mesh3d>()
114                .insert((Mesh2d(mesh_handle), MeshMaterial2d(material_handle.clone())));
115        }
116    }
117}
118
119/// This custom material uses barycentric coordinates from
120/// `ATTRIBUTE_BARYCENTRIC` to shade a white border around each triangle. The
121/// thickness of the border is animated using the global time shader uniform.
122#[derive(Asset, TypePath, AsBindGroup, Debug, Clone)]
123struct CustomMaterial {}
124
125impl Material2d for CustomMaterial {
126    fn vertex_shader() -> ShaderRef {
127        SHADER_ASSET_PATH.into()
128    }
129    fn fragment_shader() -> ShaderRef {
130        SHADER_ASSET_PATH.into()
131    }
132
133    fn specialize(
134        descriptor: &mut RenderPipelineDescriptor,
135        layout: &MeshVertexBufferLayoutRef,
136        _key: Material2dKey<Self>,
137    ) -> Result<(), SpecializedMeshPipelineError> {
138        let vertex_layout = layout.0.get_layout(&[
139            Mesh::ATTRIBUTE_POSITION.at_shader_location(0),
140            Mesh::ATTRIBUTE_COLOR.at_shader_location(1),
141            ATTRIBUTE_BARYCENTRIC.at_shader_location(2),
142        ])?;
143        descriptor.vertex.buffers = vec![vertex_layout];
144        Ok(())
145    }
146}
gltf_extension_mesh_2d/gltf_extension_mesh_2d.rs

gltf_extension_mesh_2d/
gltf_extension_mesh_2d.rs
