Bevy App Compute

Dispatch and run compute shaders on bevy from App World .

Getting Started

Add the following line to your Cargo.toml

toml [dependencies] bevy_app_compute = "0.10.3"

Usage

Setup

Declare your shaders in structs implementing ComputeShader. The shader() fn should point to your shader source code. You need to derive TypeUuid as well and assign a unique Uuid:

```rust

[derive(TypeUuid)]

[uuid = "2545ae14-a9bc-4f03-9ea4-4eb43d1075a7"]

struct SimpleShader;

impl ComputeShader for SimpleShader { fn shader() -> ShaderRef { "shaders/simple.wgsl".into() } } ```

Next, declare a struct implementing ComputeWorker to declare the bindings and the logic of your worker:

```rust

[derive(Resource)]

struct SimpleComputeWorker;

impl ComputeWorker for SimpleComputeWorker { fn build(world: &mut World) -> AppComputeWorker { let worker = AppComputeWorkerBuilder::new(world) // Add a uniform variable .add_uniform("uni", &5.)

        // Add a staging buffer, it will be available from
        // both CPU and GPU land.
        .add_staging("values", &[1., 2., 3., 4.])

        // Create a compute pass from your compute shader
        // and define used variables
        .add_pass::<SimpleShader>([4, 1, 1], &["uni", "values"])
        .build();

    worker
}

}

```

Don't forget to add a shader file to your assets/ folder:

```rust

@group(0) @binding(0) var uni: f32;

@group(0) @binding(1) var my_storage: array;

@compute @workgroupsize(1) fn main(@builtin(globalinvocationid) invocationid: vec3) { mystorage[invocationid.x] = mystorage[invocationid.x] + uni; } ```

Add the AppComputePlugin plugin to your app, as well as one AppComputeWorkerPlugin per struct implementing ComputeWorker:

```rust use bevy::prelude::*; use bevyappcompute::AppComputePlugin;

fn main() { App::new() .addplugin(AppComputePlugin) .addplugin(AppComputeWorkerPlugin::::default()); } ```

Your compute worker will now run every frame, during the PostUpdate stage. To read/write from it, use the AppComputeWorker<T> resource!

```rust fn mysystem( mut computeworker: ResMut> ) { if !compute_worker.available() { return; };

let result: Vec<f32> = compute_worker.read_vec("values");

compute_worker.write_slice("values", [2., 3., 4., 5.]);

println!("got {:?}", result)

} ```

(see simple.rs)

Multiple passes

You can have multiple passes without having to copy data back to the CPU in between:

``rust let worker = AppComputeWorkerBuilder::new(world) .add_uniform("value", &3.) .add_storage("input", &[1., 2., 3., 4.]) .add_staging("output", &[0f32; 4]) // add each item +valuefrominputtooutput .add_pass::<FirstPassShader>([4, 1, 1], &["value", "input", "output"]) // multiply each element ofoutput` by itself .add_pass::([4, 1, 1], &["output"]) .build();

// the `output` buffer will contain [16.0, 25.0, 36.0, 49.0]

```

(see multi_pass.rs)

One shot computes

You can configure your worker to execute only when requested:

```rust let worker = AppComputeWorkerBuilder::new(world) .adduniform("uni", &5.) .addstaging("values", &[1., 2., 3., 4.]) .add_pass::([4, 1, 1], &["uni", "values"])

// This `one_shot()` function will configure your worker accordingly
.one_shot()
.build();

```

Then, you can call execute() on your worker when you are ready to execute it:

```rust // Execute it only when the left mouse button is pressed. fn onclickcompute( buttons: Res>, mut computeworker: ResMut> ) { if !buttons.justpressed(MouseButton::Left) { return; }

compute_worker.execute();

} ```

It will run at the end of the current frame, and you'll be able to read the data in the next frame.

(see one_shot.rs)

Examples

See examples

Features being worked upon

• Ability to read/write between compute passes.
• add more options to the api, like deciding BufferUsages or size of buffers.
• Optimization. Right now the code is a complete mess.
• Tests. This badly needs tests.

Bevy version mapping

|Bevy|bevyappcompute| |---|---| |main|main| |0.10|0.10.3|