docs/bevy/examples/gltf/custom_gltf_vertex_attribute.rs 3.3 K · 96 lines · raw · history

1 //! Renders a glTF mesh in 2D with a custom vertex attribute.
2
3 use bevy::{
4 gltf::GltfPlugin,
5 mesh::{MeshVertexAttribute, MeshVertexBufferLayoutRef},
6 prelude::*,
7 reflect::TypePath,
8 render::render_resource::*,
9 shader::ShaderRef,
10 sprite_render::{Material2d, Material2dKey, Material2dPipeline, Material2dPlugin},
11 };
12
13 /// This example uses a shader source file from the assets subdirectory
14 const SHADER_ASSET_PATH: &str = "shaders/custom_gltf_2d.wesl";
15
16 /// This vertex attribute supplies barycentric coordinates for each triangle.
17 ///
18 /// Each component of the vector corresponds to one corner of a triangle. It's
19 /// equal to 1.0 in that corner and 0.0 in the other two. Hence, its value in
20 /// the fragment shader indicates proximity to a corner or the opposite edge.
21 const ATTRIBUTE_BARYCENTRIC: MeshVertexAttribute =
22 MeshVertexAttribute::new("Barycentric", 2137464976, VertexFormat::Float32x3);
23
24 fn main() {
25 App::new()
26 .insert_resource(GlobalAmbientLight {
27 color: Color::WHITE,
28 brightness: 1.0 / 5.0f32,
29 ..default()
30 })
31 .add_plugins((
32 DefaultPlugins.set(
33 GltfPlugin::default()
34 // Map a custom glTF attribute name to a `MeshVertexAttribute`.
35 // The glTF file used here has an attribute name with *two*
36 // underscores: __BARYCENTRIC
37 // One is stripped to do the comparison here.
38 .add_custom_vertex_attribute("_BARYCENTRIC", ATTRIBUTE_BARYCENTRIC),
39 ),
40 Material2dPlugin::<CustomMaterial>::default(),
41 ))
42 .add_systems(Startup, setup)
43 .run();
44 }
45
46 fn setup(
47 mut commands: Commands,
48 asset_server: Res<AssetServer>,
49 mut materials: ResMut<Assets<CustomMaterial>>,
50 ) {
51 // Add a mesh loaded from a glTF file. This mesh has data for `ATTRIBUTE_BARYCENTRIC`.
52 let mesh = asset_server.load(
53 GltfAssetLabel::Primitive {
54 mesh: 0,
55 primitive: 0,
56 }
57 .from_asset("models/barycentric/barycentric.gltf"),
58 );
59 commands.spawn((
60 Mesh2d(mesh),
61 MeshMaterial2d(materials.add(CustomMaterial {})),
62 Transform::from_scale(150.0 * Vec3::ONE),
63 ));
64
65 commands.spawn(Camera2d);
66 }
67
68 /// This custom material uses barycentric coordinates from
69 /// `ATTRIBUTE_BARYCENTRIC` to shade a white border around each triangle. The
70 /// thickness of the border is animated using the global time shader uniform.
71 #[derive(Asset, TypePath, AsBindGroup, Debug, Clone)]
72 struct CustomMaterial {}
73
74 impl Material2d for CustomMaterial {
75 fn vertex_shader() -> ShaderRef {
76 SHADER_ASSET_PATH.into()
77 }
78 fn fragment_shader() -> ShaderRef {
79 SHADER_ASSET_PATH.into()
80 }
81
82 fn specialize(
83 _pipeline: &Material2dPipeline,
84 descriptor: &mut RenderPipelineDescriptor,
85 layout: &MeshVertexBufferLayoutRef,
86 _key: Material2dKey<Self>,
87 ) -> Result<(), SpecializedMeshPipelineError> {
88 let vertex_layout = layout.0.get_layout(&[
89 Mesh::ATTRIBUTE_POSITION.at_shader_location(0),
90 Mesh::ATTRIBUTE_COLOR.at_shader_location(1),
91 ATTRIBUTE_BARYCENTRIC.at_shader_location(2),
92 ])?;
93 descriptor.vertex.buffers = vec![vertex_layout];
94 Ok(())
95 }
96 }