a861452d68
# Objective Because of mesh preprocessing, users cannot rely on `@builtin(instance_index)` in order to reference external data, as the instance index is not stable, either from frame to frame or relative to the total spawn order of mesh instances. ## Solution Add a user supplied mesh index that can be used for referencing external data when drawing instanced meshes. Closes #13373 ## Testing Benchmarked `many_cubes` showing no difference in total frame time. ## Showcase https://github.com/user-attachments/assets/80620147-aafc-4d9d-a8ee-e2149f7c8f3b --------- Co-authored-by: IceSentry <IceSentry@users.noreply.github.com>
115 lines
3.2 KiB
Rust
115 lines
3.2 KiB
Rust
//! This example demonstrates how to use a storage buffer with `AsBindGroup` in a custom material.
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use bevy::{
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prelude::*,
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reflect::TypePath,
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render::{
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mesh::MeshTag,
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render_resource::{AsBindGroup, ShaderRef},
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storage::ShaderStorageBuffer,
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},
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};
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const SHADER_ASSET_PATH: &str = "shaders/storage_buffer.wgsl";
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fn main() {
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App::new()
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.add_plugins((DefaultPlugins, MaterialPlugin::<CustomMaterial>::default()))
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.add_systems(Startup, setup)
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.add_systems(Update, update)
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.run();
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}
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/// set up a simple 3D scene
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fn setup(
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mut commands: Commands,
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mut meshes: ResMut<Assets<Mesh>>,
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mut buffers: ResMut<Assets<ShaderStorageBuffer>>,
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mut materials: ResMut<Assets<CustomMaterial>>,
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) {
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// Example data for the storage buffer
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let color_data: Vec<[f32; 4]> = vec![
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[1.0, 0.0, 0.0, 1.0],
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[0.0, 1.0, 0.0, 1.0],
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[0.0, 0.0, 1.0, 1.0],
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[1.0, 1.0, 0.0, 1.0],
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[0.0, 1.0, 1.0, 1.0],
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];
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let colors = buffers.add(ShaderStorageBuffer::from(color_data));
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let mesh_handle = meshes.add(Cuboid::from_size(Vec3::splat(0.3)));
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// Create the custom material with the storage buffer
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let material_handle = materials.add(CustomMaterial {
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colors: colors.clone(),
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});
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commands.insert_resource(CustomMaterialHandle(material_handle.clone()));
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// Spawn cubes with the custom material
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let mut current_color_id: u32 = 0;
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for i in -6..=6 {
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for j in -3..=3 {
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commands.spawn((
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Mesh3d(mesh_handle.clone()),
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MeshMaterial3d(material_handle.clone()),
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MeshTag(current_color_id % 5),
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Transform::from_xyz(i as f32, j as f32, 0.0),
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));
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current_color_id += 1;
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}
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}
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// Camera
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commands.spawn((
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Camera3d::default(),
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Transform::from_xyz(0.0, 0.0, 10.0).looking_at(Vec3::ZERO, Vec3::Y),
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));
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}
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// Update the material color by time
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fn update(
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time: Res<Time>,
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material_handles: Res<CustomMaterialHandle>,
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mut materials: ResMut<Assets<CustomMaterial>>,
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mut buffers: ResMut<Assets<ShaderStorageBuffer>>,
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) {
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let material = materials.get_mut(&material_handles.0).unwrap();
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let buffer = buffers.get_mut(&material.colors).unwrap();
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buffer.set_data(
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(0..5)
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.map(|i| {
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let t = time.elapsed_secs() * 5.0;
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[
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ops::sin(t + i as f32) / 2.0 + 0.5,
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ops::sin(t + i as f32 + 2.0) / 2.0 + 0.5,
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ops::sin(t + i as f32 + 4.0) / 2.0 + 0.5,
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1.0,
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]
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})
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.collect::<Vec<[f32; 4]>>()
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.as_slice(),
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);
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}
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// Holds handles to the custom materials
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#[derive(Resource)]
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struct CustomMaterialHandle(Handle<CustomMaterial>);
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// This struct defines the data that will be passed to your shader
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#[derive(Asset, TypePath, AsBindGroup, Debug, Clone)]
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struct CustomMaterial {
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#[storage(0, read_only)]
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colors: Handle<ShaderStorageBuffer>,
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}
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impl Material for CustomMaterial {
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fn vertex_shader() -> ShaderRef {
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SHADER_ASSET_PATH.into()
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}
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fn fragment_shader() -> ShaderRef {
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SHADER_ASSET_PATH.into()
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}
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}
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