ios - iOS Swift Metal SKRenderer 离屏渲染

Question

我正在尝试使用 渲染SKScene屏幕外SKRenderer，然后将其用于 SceneKit SCNMaterial。myScene在这里，是SKScene. 我已经像这样设置了渲染器；

var device:MTLDevice!
var commandQueue: MTLCommandQueue!
var renderer: SKRenderer!
var offscreenTexture: MTLTexture!

let rgbColorSpace = CGColorSpaceCreateDeviceRGB()
let bytesPerPixel = Int(4)
let bitsPerComponent = Int(8)
let bitsPerPixel:Int = 32
var textureSizeX:Int = Int(myScene.width)
var textureSizeY:Int = Int(myScene.height)

func setupMetal() {

    if let defaultMtlDevice = MTLCreateSystemDefaultDevice() {
        device = defaultMtlDevice
        commandQueue = device.makeCommandQueue()
        renderer = SKRenderer(device: device)
    } else {
        fatalError("iOS simulator does not support Metal, this example can only be run on a real device.")
    }

}

func setupMetalUsingDevice(_ device: MTLDevice?) {

    guard device != nil else {
        setupMetal()
        return
    }

    self.device = device
    commandQueue = device!.makeCommandQueue()
    renderer = SKRenderer(device: device!)

}

func setupTexture() {

    var rawData0 = [UInt8](repeating: 0, count: Int(textureSizeX) * Int(textureSizeY) * 4)

    let bytesPerRow = 4 * Int(textureSizeX)
    let bitmapInfo = CGBitmapInfo.byteOrder32Big.rawValue | CGImageAlphaInfo.premultipliedLast.rawValue

    let context = CGContext(data: &rawData0, width: Int(textureSizeX), height: Int(textureSizeY), bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: rgbColorSpace, bitmapInfo: bitmapInfo)!
    context.setFillColor(UIColor.green.cgColor)
    context.fill(CGRect(x: 0, y: 0, width: CGFloat(textureSizeX), height: CGFloat(textureSizeY)))

    let textureDescriptor = MTLTextureDescriptor.texture2DDescriptor(pixelFormat: MTLPixelFormat.rgba8Unorm, width: Int(textureSizeX), height: Int(textureSizeY), mipmapped: false)

    textureDescriptor.usage = MTLTextureUsage(rawValue: MTLTextureUsage.renderTarget.rawValue | MTLTextureUsage.shaderRead.rawValue)

    let textureA = device.makeTexture(descriptor: textureDescriptor)!

    let region = MTLRegionMake2D(0, 0, Int(textureSizeX), Int(textureSizeY))
    textureA.replace(region: region, mipmapLevel: 0, withBytes: &rawData0, bytesPerRow: Int(bytesPerRow))

    offscreenTexture = textureA

}

func doRender() {

    //rendering to a MTLTexture, so the viewport is the size of this texture
    let viewport = CGRect(x: 0, y: 0, width: CGFloat(textureSizeX), height: CGFloat(textureSizeY))

    //write to offscreenTexture, clear the texture before rendering using green, store the result
    let renderPassDescriptor = MTLRenderPassDescriptor()
    renderPassDescriptor.renderTargetWidth = textureSizeX
    renderPassDescriptor.renderTargetHeight = textureSizeY
    renderPassDescriptor.defaultRasterSampleCount = 1
    renderPassDescriptor.colorAttachments[0].texture = offscreenTexture
    renderPassDescriptor.colorAttachments[0].loadAction = .clear
    renderPassDescriptor.colorAttachments[0].clearColor = MTLClearColorMake(0, 1, 0, 1.0)
    renderPassDescriptor.colorAttachments[0].storeAction = .store

    guard let commandBuffer = commandQueue.makeCommandBuffer() else {
        return
    }

    renderer.scene = myScene

    renderer.scene?.isPaused = false

    renderer.render(withViewport: viewport, commandBuffer: commandBuffer, renderPassDescriptor: renderPassDescriptor)

    commandBuffer.commit()

}

func createMaterial() {
    let material = SCNMaterial()
    material.diffuse.contents = viewController.offscreenTexture
    material.blendMode = blendMode
    geometry?.materials = [material]
}

一旦doRender()被调用以开始渲染 myScene，我会收到以下错误：

-[MTLRenderPipelineDescriptorInternal validateWithDevice:]，第 2558 行：错误“为渲染目标 0 启用了混合；但是，此渲染目标的像素格式 MTLPixelFormatInvalid 不可混合。

请有人告诉我我做错了什么以及如何让事情正常工作？

标签： iossprite-kitscenekitmetal