d74533b407
# Objective The objective is to be able to load data from "application-specific" (see glTF spec 3.7.2.1.) vertex attribute semantics from glTF files into Bevy meshes. ## Solution Rather than probe the glTF for the specific attributes supported by Bevy, this PR changes the loader to iterate through all the attributes and map them onto `MeshVertexAttribute`s. This mapping includes all the previously supported attributes, plus it is now possible to add mappings using the `add_custom_vertex_attribute()` method on `GltfPlugin`. ## Changelog - Add support for loading custom vertex attributes from glTF files. - Add the `custom_gltf_vertex_attribute.rs` example to illustrate loading custom vertex attributes. ## Migration Guide - If you were instantiating `GltfPlugin` using the unit-like struct syntax, you must instead use `GltfPlugin::default()` as the type is no longer unit-like.
84 lines
3.0 KiB
Rust
84 lines
3.0 KiB
Rust
//! Renders a glTF mesh in 2D with a custom vertex attribute.
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use bevy::gltf::GltfPlugin;
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use bevy::prelude::*;
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use bevy::reflect::TypeUuid;
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use bevy::render::mesh::{MeshVertexAttribute, MeshVertexBufferLayout};
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use bevy::render::render_resource::*;
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use bevy::sprite::{
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Material2d, Material2dKey, Material2dPlugin, MaterialMesh2dBundle, Mesh2dHandle,
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};
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/// This vertex attribute supplies barycentric coordinates for each triangle.
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/// Each component of the vector corresponds to one corner of a triangle. It's
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/// equal to 1.0 in that corner and 0.0 in the other two. Hence, its value in
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/// the fragment shader indicates proximity to a corner or the opposite edge.
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const ATTRIBUTE_BARYCENTRIC: MeshVertexAttribute =
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MeshVertexAttribute::new("Barycentric", 2137464976, VertexFormat::Float32x3);
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fn main() {
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App::new()
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.insert_resource(AmbientLight {
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color: Color::WHITE,
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brightness: 1.0 / 5.0f32,
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})
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.add_plugins(
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DefaultPlugins.set(
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GltfPlugin::default()
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// Map a custom glTF attribute name to a `MeshVertexAttribute`.
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.add_custom_vertex_attribute("_BARYCENTRIC", ATTRIBUTE_BARYCENTRIC),
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),
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)
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.add_plugin(Material2dPlugin::<CustomMaterial>::default())
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.add_systems(Startup, setup)
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.run();
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}
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fn setup(
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mut commands: Commands,
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asset_server: Res<AssetServer>,
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mut materials: ResMut<Assets<CustomMaterial>>,
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) {
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// Add a mesh loaded from a glTF file. This mesh has data for `ATTRIBUTE_BARYCENTRIC`.
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let mesh = asset_server.load("models/barycentric/barycentric.gltf#Mesh0/Primitive0");
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commands.spawn(MaterialMesh2dBundle {
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mesh: Mesh2dHandle(mesh),
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material: materials.add(CustomMaterial {}),
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transform: Transform::from_scale(150.0 * Vec3::ONE),
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..default()
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});
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// Add a camera
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commands.spawn(Camera2dBundle { ..default() });
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}
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/// This custom material uses barycentric coordinates from
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/// `ATTRIBUTE_BARYCENTRIC` to shade a white border around each triangle. The
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/// thickness of the border is animated using the global time shader uniform.
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#[derive(AsBindGroup, TypeUuid, Debug, Clone)]
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#[uuid = "50ffce9e-1582-42e9-87cb-2233724426c0"]
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struct CustomMaterial {}
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impl Material2d for CustomMaterial {
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fn fragment_shader() -> ShaderRef {
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"shaders/custom_gltf_2d.wgsl".into()
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}
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fn vertex_shader() -> ShaderRef {
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"shaders/custom_gltf_2d.wgsl".into()
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}
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fn specialize(
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descriptor: &mut RenderPipelineDescriptor,
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layout: &MeshVertexBufferLayout,
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_key: Material2dKey<Self>,
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) -> Result<(), SpecializedMeshPipelineError> {
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let vertex_layout = layout.get_layout(&[
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Mesh::ATTRIBUTE_POSITION.at_shader_location(0),
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Mesh::ATTRIBUTE_COLOR.at_shader_location(1),
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ATTRIBUTE_BARYCENTRIC.at_shader_location(2),
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])?;
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descriptor.vertex.buffers = vec![vertex_layout];
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Ok(())
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}
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}
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