e6ba9a6d18
# Objective Closes #18075 In order to enable a number of patterns for dynamic materials in the engine, it's necessary to decouple the renderer from the `Material` trait. This opens the possibility for: - Materials that aren't coupled to `AsBindGroup`. - 2d using the underlying 3d bindless infrastructure. - Dynamic materials that can change their layout at runtime. - Materials that aren't even backed by a Rust struct at all. ## Solution In short, remove all trait bounds from render world material systems and resources. This means moving a bunch of stuff onto `MaterialProperties` and engaging in some hacks to make specialization work. Rather than storing the bind group data in `MaterialBindGroupAllocator`, right now we're storing it in a closure on `MaterialProperties`. TBD if this has bad performance characteristics. ## Benchmarks - `many_cubes`: `cargo run --example many_cubes --release --features=bevy/trace_tracy -- --vary-material-data-per-instance`:  - @DGriffin91's Caldera `cargo run --release --features=bevy/trace_tracy -- --random-materials`  - @DGriffin91's Caldera with 20 unique material types (i.e. `MaterialPlugin<M>`) and random materials per mesh `cargo run --release --features=bevy/trace_tracy -- --random-materials`  ### TODO - We almost certainly lost some parallelization from removing the type params that could be gained back from smarter iteration. - Test all the things that could have broken. - ~Fix meshlets~ ## Showcase See [the example](https://github.com/bevyengine/bevy/pull/19667/files#diff-9d768cfe1c3aa81eff365d250d3cbe5a63e8df63e81dd85f64c3c3cd993f6d94) for a custom material implemented without the use of the `Material` trait and thus `AsBindGroup`.  --------- Co-authored-by: IceSentry <IceSentry@users.noreply.github.com> Co-authored-by: IceSentry <c.giguere42@gmail.com>
105 lines
3.1 KiB
Rust
105 lines
3.1 KiB
Rust
//! A shader that uses "shaders defs", which selectively toggle parts of a shader.
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use bevy::{
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pbr::{MaterialPipeline, MaterialPipelineKey},
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prelude::*,
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reflect::TypePath,
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render::{
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mesh::MeshVertexBufferLayoutRef,
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render_resource::{
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AsBindGroup, RenderPipelineDescriptor, ShaderRef, SpecializedMeshPipelineError,
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},
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},
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};
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/// This example uses a shader source file from the assets subdirectory
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const SHADER_ASSET_PATH: &str = "shaders/shader_defs.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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.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 materials: ResMut<Assets<CustomMaterial>>,
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) {
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// blue cube
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commands.spawn((
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Mesh3d(meshes.add(Cuboid::default())),
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MeshMaterial3d(materials.add(CustomMaterial {
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color: LinearRgba::BLUE,
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is_red: false,
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})),
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Transform::from_xyz(-1.0, 0.5, 0.0),
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));
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// red cube (with green color overridden by the IS_RED "shader def")
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commands.spawn((
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Mesh3d(meshes.add(Cuboid::default())),
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MeshMaterial3d(materials.add(CustomMaterial {
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color: LinearRgba::GREEN,
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is_red: true,
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})),
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Transform::from_xyz(1.0, 0.5, 0.0),
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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(-2.0, 2.5, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
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));
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}
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impl Material for CustomMaterial {
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fn fragment_shader() -> ShaderRef {
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SHADER_ASSET_PATH.into()
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}
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fn specialize(
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_pipeline: &MaterialPipeline,
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descriptor: &mut RenderPipelineDescriptor,
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_layout: &MeshVertexBufferLayoutRef,
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key: MaterialPipelineKey<Self>,
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) -> Result<(), SpecializedMeshPipelineError> {
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if key.bind_group_data.is_red == 1 {
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let fragment = descriptor.fragment.as_mut().unwrap();
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fragment.shader_defs.push("IS_RED".into());
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}
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Ok(())
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}
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}
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// This is the struct that will be passed to your shader
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#[derive(Asset, TypePath, AsBindGroup, Debug, Clone)]
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#[bind_group_data(CustomMaterialKey)]
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struct CustomMaterial {
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#[uniform(0)]
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color: LinearRgba,
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is_red: bool,
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}
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// This key is used to identify a specific permutation of this material pipeline.
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// In this case, we specialize on whether or not to configure the "IS_RED" shader def.
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// Specialization keys should be kept as small / cheap to hash as possible,
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// as they will be used to look up the pipeline for each drawn entity with this material type,
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// Which is why they are required to be `bytemuck::Pod` and `bytemuck::Zeroable` for materials
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// that use the `AsBindGroup` derive macro.
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#[repr(C)]
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#[derive(Eq, PartialEq, Hash, Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
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struct CustomMaterialKey {
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is_red: u32,
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}
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impl From<&CustomMaterial> for CustomMaterialKey {
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fn from(material: &CustomMaterial) -> Self {
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Self {
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is_red: material.is_red as u32,
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}
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}
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}
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