Examples of using Compute with RealityView and MetalView

[potmo]

Would you be interested in taking PRs for examples showing how to display a texture created by a compute shader in a RealityView and a MetalView? I've been trying out some code and I can clean it up to make it into stand alone examples in the Examples-folder if that would be of any help.

[schwa]

Happy to take a look. It would be great if the sample was pretty small though.

[potmo]

See PR #11 for a RealityKit example.

I can also make an example of how to use a MTKView where you can draw to the entire view and not just a texture on a plane. Maybe the GameOfLife example can be reused for that?
One thing I'm not really sure on how to do is that the GameOfLife example uses two textures that swaps between being input and output but with both RealityView and MTKView you have just one output texture. I guess one needs to blit from the resulting texture to the actual output texture like:

guard let blitEncoder = commandBuffer.makeBlitCommandEncoder() else {
   fatalError("could not create blit encoder")
}

blitEncoder.copy(from: outputTexture, to: renderTexture)
blitEncoder.endEncoding()

but then again one needs either to create a new MTLCommandBuffer or expose the one Compute.Task already have.

[potmo]

I tested making Task.commandBuffer public and then adding a blit in the end like this.

try compute.task { task in
    try task { dispatch in
        try dispatch(pipeline: somePipeline,
                     threadgroupsPerGrid: MTLSize(width: outputTexture.width, height: outputTexture.height, depth: 1),
                     threadsPerThreadgroup: MTLSize(width: threadsPerThreadgroupWidth, height: threadsPerThreadgroupHeight, depth: 1))
    }

    guard let blitEncoder = task.commandBuffer.makeBlitCommandEncoder() else {
       fatalError("could not create blir encoder")
    }

    blitEncoder.copy(from: outputTexture, to: renderTexture)
    blitEncoder.endEncoding()
}

It seems to work but strangely i get worse performance than just creating a new command buffer and doing the blit on that:

try compute.task { task in
    try task { dispatch in
        try dispatch(pipeline: randomEat,
                     threadgroupsPerGrid: MTLSize(width: outputTexture.width, height: outputTexture.height, depth: 1),
                     threadsPerThreadgroup: MTLSize(width: threadsPerThreadgroupWidth, height: threadsPerThreadgroupHeight, depth: 1))
    }
}

let commandBuffer = metalDevice.makeCommandQueue()!.makeCommandBuffer()!
commandBuffer.enqueue()

let blitEncoder = commandBuffer.makeBlitCommandEncoder()!

blitEncoder.copy(from: outputTexture, to: renderTexture)
blitEncoder.endEncoding()

commandBuffer.commit()
commandBuffer.waitUntilCompleted()