Support for storage textures on WebGPU platform

[mvaligursky]

Support for storage textures, which represent textures that can be written to by a compute shader.

New API:

Texture.constructor takes options.storage as an optional parameter, to construct a texture that is useable as a storage texture for compute shader. Ignored on WebGL.

Example

Using compute shader to fill texture with a single color:

const texture = new Texture(app.graphicsDevice, {
    name: 'outputTexture',
    width: 128,
    height: 128,
    format: PIXELFORMAT_RGBA8,
    mipmaps: false,
    storage: true
});

device.scope.resolve("outTexture").setValue(texture);

const shader = new Shader(device, {
    name: 'ComputeShader',
    shaderLanguage: SHADERLANGUAGE_WGSL,
    cshader: `

        @group(0) @binding(0) var outputTexture: texture_storage_2d<rgba8unorm, write>;

        @compute @workgroup_size(1, 1, 1)
        fn main(@builtin(global_invocation_id) global_id : vec3u) {

            let clearColor: vec4<f32> = vec4<f32>(1.0, 0.0, 0.0, 1.0);
            textureStore(outputTexture, vec2<i32>(global_id.xy), clearColor);
        }
    `
});

// data biding for the shader using a single storage texture (no UBs nor other textures)
// Note: the API here is temporary (the `impl`)
shader.impl.computeBindGroupFormat = new BindGroupFormat(device,[], [], [
    new BindStorageTextureFormat('outTexture', PIXELFORMAT_RGBA8, TEXTUREDIMENSION_2D),
], {
    compute: true
});

const compute = new Compute(device, this.shader);

// run the compute shader
compute.dispatch(texture.width, texture.height);