SceneKitMetalSetupMetalResources.swift

func setupMetalResources() {
    guard let device = scnView.device else {
        assertionFailure()
        return
    }
    
    // We're drawing a simple triangle so we only need a position and a color
    struct TriangleVertex {
        var position: vector_float4
        var color: vector_float4
    }
    
    // Define the triangle's vertices and colors
    let vertices: [TriangleVertex] = [
        // Top triangle, red color
        TriangleVertex(position: vector_float4( 0.0, 0.5, 0, 1), color: vector_float4(1, 0, 0, 1)),
        // Bottom left triangle, green color
        TriangleVertex(position: vector_float4( -0.5, -0.5, 0, 1), color: vector_float4(0, 1, 0, 1)),
        // Bottom right triangle, blue color
        TriangleVertex(position: vector_float4( 0.5, -0.5, 0, 1), color: vector_float4(0, 0, 1, 1))
    ]
    // Create the vertex buffer
    self.vertexBuffer = device.makeBuffer(
        bytes: vertices,
        length: MemoryLayout<TriangleVertex>.size * vertices.count,
        options: .cpuCacheModeWriteCombined)
    
    // Set up the shaders
    let library = device.makeDefaultLibrary()
    let vertexFunc = library?.makeFunction(name: "passthrough_vertex")
    let fragmentFunc = library?.makeFunction(name: "passthrough_fragment")
    
    // Create the pipeline descriptor
    let pipelineDescriptor = MTLRenderPipelineDescriptor()
    pipelineDescriptor.vertexFunction = vertexFunc
    pipelineDescriptor.fragmentFunction = fragmentFunc
    // Use SCNView's pixel format
    pipelineDescriptor.colorAttachments[0].pixelFormat = scnView.colorPixelFormat
    pipelineDescriptor.depthAttachmentPixelFormat = scnView.depthPixelFormat
    
    guard let pipeline = try? device.makeRenderPipelineState(descriptor: pipelineDescriptor)
    else {
        assertionFailure()
        return
    }
    
    self.pipelineState = pipeline
}