我想在渲染时应用相机滤镜，我的代码是...
func session(_ session: ARSession, didUpdate frame: ARFrame) {
let image = CIImage(cvPixelBuffer: frame.capturedImage)
var r: CGFloat = 0, g: CGFloat = 0, b: CGFloat = 0, a: CGFloat = 0
color.getRed(&r, green: &g, blue: &b, alpha: &a)
filter.setDefaults()
filter.setValue(image, forKey: kCIInputImageKey)
filter.setValue(CIVector(x: r, y: 0, z: 0, w: 0), forKey: "inputRVector")
filter.setValue(CIVector(x: 0, y: g, z: 0, w: 0), forKey: "inputGVector")
filter.setValue(CIVector(x: 0, y: 0, z: b, w: 0), forKey: "inputBVector")
filter.setValue(CIVector(x: 0, y: 0, z: 0, w: a), …