bevy/examples/shader/hot_shader_reloading.rs

use bevy::{
    prelude::*,
    reflect::TypeUuid,
    render::{
        mesh::shape,
        pipeline::{PipelineDescriptor, RenderPipeline},
        render_graph::{base, AssetRenderResourcesNode, RenderGraph},
        renderer::RenderResources,
        shader::ShaderStages,
    },
};

/// This example illustrates how to load shaders such that they can be
/// edited while the example is still running.
fn main() {
    App::build()
        .add_plugins(DefaultPlugins)
        .add_asset::<MyMaterial>()
        .add_startup_system(setup.system())
        .run();
}

#[derive(RenderResources, Default, TypeUuid)]
#[uuid = "3bf9e364-f29d-4d6c-92cf-93298466c620"]
struct MyMaterial {
    pub color: Color,
}

fn setup(
    commands: &mut Commands,
    asset_server: ResMut<AssetServer>,
    mut pipelines: ResMut<Assets<PipelineDescriptor>>,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<MyMaterial>>,
    mut render_graph: ResMut<RenderGraph>,
) {
    // Watch for changes
    asset_server.watch_for_changes().unwrap();

    // Create a new shader pipeline with shaders loaded from the asset directory
    let pipeline_handle = pipelines.add(PipelineDescriptor::default_config(ShaderStages {
        vertex: asset_server.load::<Shader, _>("shaders/hot.vert"),
        fragment: Some(asset_server.load::<Shader, _>("shaders/hot.frag")),
    }));

    // Add an AssetRenderResourcesNode to our Render Graph. This will bind MyMaterial resources to our shader
    render_graph.add_system_node(
        "my_material",
        AssetRenderResourcesNode::<MyMaterial>::new(true),
    );

    // Add a Render Graph edge connecting our new "my_material" node to the main pass node. This ensures "my_material" runs before the main pass
    render_graph
        .add_node_edge("my_material", base::node::MAIN_PASS)
        .unwrap();

    // Create a new material
    let material = materials.add(MyMaterial {
        color: Color::rgb(0.0, 0.8, 0.0),
    });

    // Setup our world
    commands
        // cube
        .spawn(MeshBundle {
            mesh: meshes.add(Mesh::from(shape::Cube { size: 2.0 })),
            render_pipelines: RenderPipelines::from_pipelines(vec![RenderPipeline::new(
                pipeline_handle,
            )]),
            transform: Transform::from_xyz(0.0, 0.0, 0.0),
            ..Default::default()
        })
        .with(material)
        // camera
        .spawn(PerspectiveCameraBundle {
            transform: Transform::from_xyz(3.0, 5.0, -8.0)
                .looking_at(Vec3::default(), Vec3::unit_y()),
            ..Default::default()
        });
}