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shader_defs.rs
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shader_defs.rs
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//! A shader that uses "shaders defs", which selectively toggle parts of a shader.
use bevy::{
pbr::{MaterialPipeline, MaterialPipelineKey},
prelude::*,
reflect::TypePath,
render::{
mesh::MeshVertexBufferLayout,
render_resource::{
AsBindGroup, RenderPipelineDescriptor, ShaderRef, SpecializedMeshPipelineError,
},
},
};
fn main() {
App::new()
.add_plugins((DefaultPlugins, MaterialPlugin::<CustomMaterial>::default()))
.add_systems(Startup, setup)
.run();
}
/// set up a simple 3D scene
fn setup(
mut commands: Commands,
mut meshes: ResMut<Assets<Mesh>>,
mut materials: ResMut<Assets<CustomMaterial>>,
) {
// blue cube
commands.spawn(MaterialMeshBundle {
mesh: meshes.add(Cuboid::default()),
transform: Transform::from_xyz(-1.0, 0.5, 0.0),
material: materials.add(CustomMaterial {
color: Color::BLUE,
is_red: false,
}),
..default()
});
// red cube (with green color overridden by the IS_RED "shader def")
commands.spawn(MaterialMeshBundle {
mesh: meshes.add(Cuboid::default()),
transform: Transform::from_xyz(1.0, 0.5, 0.0),
material: materials.add(CustomMaterial {
color: Color::GREEN,
is_red: true,
}),
..default()
});
// camera
commands.spawn(Camera3dBundle {
transform: Transform::from_xyz(-2.0, 2.5, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
..default()
});
}
impl Material for CustomMaterial {
fn fragment_shader() -> ShaderRef {
"shaders/shader_defs.wgsl".into()
}
fn specialize(
_pipeline: &MaterialPipeline<Self>,
descriptor: &mut RenderPipelineDescriptor,
_layout: &MeshVertexBufferLayout,
key: MaterialPipelineKey<Self>,
) -> Result<(), SpecializedMeshPipelineError> {
if key.bind_group_data.is_red {
let fragment = descriptor.fragment.as_mut().unwrap();
fragment.shader_defs.push("IS_RED".into());
}
Ok(())
}
}
// This is the struct that will be passed to your shader
#[derive(Asset, TypePath, AsBindGroup, Debug, Clone)]
#[bind_group_data(CustomMaterialKey)]
struct CustomMaterial {
#[uniform(0)]
color: Color,
is_red: bool,
}
// This key is used to identify a specific permutation of this material pipeline.
// In this case, we specialize on whether or not to configure the "IS_RED" shader def.
// Specialization keys should be kept as small / cheap to hash as possible,
// as they will be used to look up the pipeline for each drawn entity with this material type.
#[derive(Eq, PartialEq, Hash, Clone)]
struct CustomMaterialKey {
is_red: bool,
}
impl From<&CustomMaterial> for CustomMaterialKey {
fn from(material: &CustomMaterial) -> Self {
Self {
is_red: material.is_red,
}
}
}