Renderer_Step4.swift

Renderer_Step4.swift

import MetalKit
import SwiftUI

class Renderer: NSObject, MTKViewDelegate {
    var device: MTLDevice!
    var commandQueue: MTLCommandQueue!
    var pipelineState: MTLRenderPipelineState!
    var time: Float = 0.0

    init(device: MTLDevice) {
        super.init()
        self.device = device
        self.commandQueue = device.makeCommandQueue()
        self.setupPipeline()
    }

    func setupPipeline() {
        let library = device.makeDefaultLibrary()
        let vertexFunction = library?.makeFunction(name: "circle_vertex")
        let fragmentFunction = library?.makeFunction(name: "circle_fragment")

        let pipelineDescriptor = MTLRenderPipelineDescriptor()
        pipelineDescriptor.vertexFunction = vertexFunction
        pipelineDescriptor.fragmentFunction = fragmentFunction
        pipelineDescriptor.colorAttachments[0].pixelFormat = .bgra8Unorm

        do {
            pipelineState = try device.makeRenderPipelineState(descriptor: pipelineDescriptor)
        } catch {
            fatalError("Failed to create pipeline state")
        }
    }

    func draw(in view: MTKView) {
        guard let drawable = view.currentDrawable else { return }
        guard let descriptor = view.currentRenderPassDescriptor else { return }

        let commandBuffer = commandQueue.makeCommandBuffer()!
        let commandEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: descriptor)!

        commandEncoder.setRenderPipelineState(pipelineState)
        commandEncoder.setFragmentBytes(&time, length: MemoryLayout<Float>.size, index: 0)

        commandEncoder.drawPrimitives(type: .triangleStrip, vertexStart: 0, vertexCount: 4)
        commandEncoder.endEncoding()

        commandBuffer.present(drawable)
        commandBuffer.commit()

        time += 0.01
    }
    
    func mtkView(_ view: MTKView, drawableSizeWillChange size: CGSize) {}
}

struct MetalView: UIViewRepresentable {
    var device: MTLDevice

    func makeUIView(context: Context) -> MTKView {
        let view = MTKView()
        view.device = device
        view.colorPixelFormat = .bgra8Unorm
        view.framebufferOnly = false
        let renderer = Renderer(device: device)
        view.delegate = renderer
        context.coordinator.renderer = renderer
        return view
    }

    func updateUIView(_ uiView: MTKView, context: Context) {}

    func makeCoordinator() -> Coordinator {
        Coordinator()
    }

    class Coordinator {
        var renderer: Renderer?
    }
}

struct ContentView: View {
    var body: some View {
        MetalView(device: MTLCreateSystemDefaultDevice()!)
            .edgesIgnoringSafeArea(.all)
    }
}

#Preview {
    ContentView()
}