docs/bevy/examples/shader_advanced/custom_vertex_attribute.rs 2.7 K · 87 lines · raw · history

1 //! A shader that reads a mesh's custom vertex attribute.
2
3 use bevy::{
4 mesh::{MeshVertexAttribute, MeshVertexBufferLayoutRef},
5 pbr::{MaterialPipeline, MaterialPipelineKey},
6 prelude::*,
7 reflect::TypePath,
8 render::render_resource::{
9 AsBindGroup, RenderPipelineDescriptor, SpecializedMeshPipelineError, VertexFormat,
10 },
11 shader::ShaderRef,
12 };
13
14 /// This example uses a shader source file from the assets subdirectory
15 const SHADER_ASSET_PATH: &str = "shaders/custom_vertex_attribute.wesl";
16
17 fn main() {
18 App::new()
19 .add_plugins((DefaultPlugins, MaterialPlugin::<CustomMaterial>::default()))
20 .add_systems(Startup, setup)
21 .run();
22 }
23
24 // A "high" random id should be used for custom attributes to ensure consistent sorting and avoid collisions with other attributes.
25 // See the MeshVertexAttribute docs for more info.
26 const ATTRIBUTE_BLEND_COLOR: MeshVertexAttribute =
27 MeshVertexAttribute::new("BlendColor", 988540917, VertexFormat::Float32x4);
28
29 /// set up a simple 3D scene
30 fn setup(
31 mut commands: Commands,
32 mut meshes: ResMut<Assets<Mesh>>,
33 mut materials: ResMut<Assets<CustomMaterial>>,
34 ) {
35 let mesh = Mesh::from(Cuboid::default())
36 // Sets the custom attribute
37 .with_inserted_attribute(
38 ATTRIBUTE_BLEND_COLOR,
39 // The cube mesh has 24 vertices (6 faces, 4 vertices per face), so we insert one BlendColor for each
40 vec![[1.0, 0.0, 0.0, 1.0]; 24],
41 );
42
43 // cube
44 commands.spawn((
45 Mesh3d(meshes.add(mesh)),
46 MeshMaterial3d(materials.add(CustomMaterial {
47 color: LinearRgba::WHITE,
48 })),
49 Transform::from_xyz(0.0, 0.5, 0.0),
50 ));
51
52 // camera
53 commands.spawn((
54 Camera3d::default(),
55 Transform::from_xyz(-2.0, 2.5, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
56 ));
57 }
58
59 // This is the struct that will be passed to your shader
60 #[derive(Asset, TypePath, AsBindGroup, Debug, Clone)]
61 struct CustomMaterial {
62 #[uniform(0)]
63 color: LinearRgba,
64 }
65
66 impl Material for CustomMaterial {
67 fn vertex_shader() -> ShaderRef {
68 SHADER_ASSET_PATH.into()
69 }
70 fn fragment_shader() -> ShaderRef {
71 SHADER_ASSET_PATH.into()
72 }
73
74 fn specialize(
75 _pipeline: &MaterialPipeline,
76 descriptor: &mut RenderPipelineDescriptor,
77 layout: &MeshVertexBufferLayoutRef,
78 _key: MaterialPipelineKey<Self>,
79 ) -> Result<(), SpecializedMeshPipelineError> {
80 let vertex_layout = layout.0.get_layout(&[
81 Mesh::ATTRIBUTE_POSITION.at_shader_location(0),
82 ATTRIBUTE_BLEND_COLOR.at_shader_location(1),
83 ])?;
84 descriptor.vertex.buffers = vec![vertex_layout];
85 Ok(())
86 }
87 }