ax-metal

Metal — GPU Programming & Migration

Quick Patterns

MTKView Setup

import MetalKit

guard let device = MTLCreateSystemDefaultDevice(),
      let queue = device.makeCommandQueue() else { fatalError("Metal not supported") }

let metalView = MTKView(frame: bounds, device: device)
metalView.colorPixelFormat = .bgra8Unorm
metalView.depthStencilPixelFormat = .depth32Float
metalView.clearColor = MTLClearColor(red: 0, green: 0, blue: 0, alpha: 1)
metalView.delegate = renderer

Render Pipeline

let library = device.makeDefaultLibrary()!
let descriptor = MTLRenderPipelineDescriptor()
descriptor.vertexFunction = library.makeFunction(name: "vertexShader")
descriptor.fragmentFunction = library.makeFunction(name: "fragmentShader")
descriptor.colorAttachments[0].pixelFormat = metalView.colorPixelFormat
descriptor.depthAttachmentPixelFormat = metalView.depthStencilPixelFormat
let pipelineState = try device.makeRenderPipelineState(descriptor: descriptor)

Draw Call

func draw(in view: MTKView) {
    guard let drawable = view.currentDrawable,
          let rpd = view.currentRenderPassDescriptor,
          let commandBuffer = commandQueue.makeCommandBuffer(),
          let encoder = commandBuffer.makeRenderCommandEncoder(descriptor: rpd) else { return }

    encoder.setRenderPipelineState(pipelineState)
    encoder.setVertexBuffer(vertexBuffer, offset: 0, index: 0)
    encoder.setFragmentTexture(texture, index: 0)
    encoder.drawPrimitives(type: .triangle, vertexStart: 0, vertexCount: vertexCount)
    encoder.endEncoding()

    commandBuffer.present(drawable)
    commandBuffer.commit()
}

Basic MSL Shader

#include <metal_stdlib>
using namespace metal;

struct VertexIn {
    float3 position [[attribute(0)]];
    float2 texCoord [[attribute(1)]];
};

struct VertexOut {
    float4 position [[position]];
    float2 texCoord;
};

struct Uniforms { float4x4 mvp; };

vertex VertexOut vertexShader(VertexIn in [[stage_in]],
                              constant Uniforms &uniforms [[buffer(1)]]) {
    VertexOut out;
    out.position = uniforms.mvp * float4(in.position, 1.0);
    out.texCoord = in.texCoord;
    return out;
}

fragment float4 fragmentShader(VertexOut in [[stage_in]],
                                texture2d<float> tex [[texture(0)]],
                                sampler samp [[sampler(0)]]) {
    return tex.sample(samp, in.texCoord);
}