我正在尝试导出在 ARSCNView 渲染过程中创建的深度纹理。为了做到这一点，我编写了一个代码，在后台使用自定义呈现 SCNScene MTLRenderPassDescriptor。当我使用“GPU Capture tool”跟踪绑定到 GPU 的资源时，我发现在SCNRenderer.render方法MTLRenderPassDescriptor中忽略了自定义。
我使用此代码将 SCNScene 渲染到屏幕外。
// Render Pass - render sceneView
renderer.scene = sceneView.scene
renderer.pointOfView = sceneView.pointOfView
renderer.render(atTime: 0, viewport: viewport, commandBuffer: commandBuffer, passDescriptor: renderPassDescriptor)
当我检查 GPU 捕获中的资源时，渲染器会生成自己的帧纹理和深度纹理，在renderPassDescriptor. 根据文件，这很奇怪。我还在没有 ARKit 会话的情况下对此进行了测试，它按预期工作（渲染器使用 中描述的纹理资源renderPassDescriptor）。我怎样才能解决这个问题？这是一个 SceneKit 错误吗？
图 1. 我在 GPU 捕获中发现深度纹理与 blit pass 无关。
这是最小工作示例。
import UIKit
import SceneKit
import ARKit
class ViewController: UIViewController, ARSCNViewDelegate, ARSessionDelegate {
@IBOutlet var sceneView: ARSCNView!
var ship: SCNNode!
var device: MTLDevice!
var renderer: SCNRenderer!
var commandQueue: MTLCommandQueue!
let textureSizeX = 2732
let textureSizeY = 2048
lazy var viewport = CGRect(x: 0, y: 0, width: CGFloat(textureSizeX), height: CGFloat(textureSizeY))
override func viewDidLoad() {
super.viewDidLoad()
// Set the view's delegate
sceneView.delegate = self
sceneView.session.delegate = self
sceneView.showsStatistics = true
sceneView.scene = SCNScene()
ship = SCNScene(named: "art.scnassets/ship.scn")?.rootNode.childNode(withName: "shipMesh", recursively: true)!
sceneView.scene.rootNode.addChildNode(ship)
// background renderer
device = MTLCreateSystemDefaultDevice()!
renderer = SCNRenderer(device: device, options: nil)
commandQueue = device.makeCommandQueue()!
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
guard let referenceImages = ARReferenceImage.referenceImages(inGroupNamed: "AR Resources", bundle: nil) else {
fatalError("Missing expected asset catalog resources.")
}
// Create a session configuration
let configuration = ARWorldTrackingConfiguration()
configuration.detectionImages = referenceImages
// Run the view's session
sceneView.session.run(configuration, options: [.resetTracking, .removeExistingAnchors])
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
// Pause the view's session
sceneView.session.pause()
}
// MARK: - ARSCNViewDelegate
// Override to create and configure nodes for anchors added to the view's session.
func renderer(_ renderer: SCNSceneRenderer, willRenderScene scene: SCNScene, atTime time: TimeInterval) {
doRender()
}
func doRender() {
let renderPassDescriptor = makeRenderPassDescriptor()
let commandBuffer = commandQueue.makeCommandBuffer()!
// Render Pass - render sceneView
renderer.scene = sceneView.scene
renderer.pointOfView = sceneView.pointOfView
renderer.render(atTime: 0, viewport: viewport, commandBuffer: commandBuffer, passDescriptor: renderPassDescriptor)
// Blit Pass - copy depth texture to buffer
let imageWidth = Int(textureSizeX)
let imageHeight = Int(textureSizeY)
let pixelCount = imageWidth * imageHeight
let depthImageBuffer = device.makeBuffer(length: 4 * pixelCount, options: .storageModeShared)!
let blitEncoder = commandBuffer.makeBlitCommandEncoder()!
blitEncoder.copy(from: renderPassDescriptor.depthAttachment.texture!,
sourceSlice: 0,
sourceLevel: 0,
sourceOrigin: MTLOriginMake(0, 0, 0),
sourceSize: MTLSizeMake(imageWidth, imageHeight, 1),
to: depthImageBuffer,
destinationOffset: 0,
destinationBytesPerRow: 4 * imageWidth,
destinationBytesPerImage: 4 * pixelCount,
options: .depthFromDepthStencil)
blitEncoder.endEncoding()
commandBuffer.commit()
// Wait until depth buffer copying is done.
commandBuffer.waitUntilCompleted()
}
func makeRenderPassDescriptor() -> MTLRenderPassDescriptor {
let renderPassDescriptor = MTLRenderPassDescriptor()
let frameBufferDescriptor = MTLTextureDescriptor.texture2DDescriptor(pixelFormat: .rgba8Unorm_srgb, width: textureSizeX, height: textureSizeY, mipmapped: false)
frameBufferDescriptor.usage = [.renderTarget, .shaderRead]
renderPassDescriptor.colorAttachments[0].texture = device.makeTexture(descriptor: frameBufferDescriptor)!
renderPassDescriptor.colorAttachments[0].loadAction = .clear
renderPassDescriptor.colorAttachments[0].storeAction = .store
renderPassDescriptor.colorAttachments[0].clearColor = MTLClearColorMake(1, 1, 1, 1.0)
let depthBufferDescriptor: MTLTextureDescriptor = MTLTextureDescriptor.texture2DDescriptor(pixelFormat: .depth32Float, width: textureSizeX, height: textureSizeY, mipmapped: false)
depthBufferDescriptor.usage = .renderTarget
renderPassDescriptor.depthAttachment.texture = device.makeTexture(descriptor: depthBufferDescriptor)
renderPassDescriptor.depthAttachment.loadAction = .clear
renderPassDescriptor.depthAttachment.storeAction = .store
return renderPassDescriptor
}
func session(_ session: ARSession, didFailWithError error: Error) {
// Present an error message to the user
}
func session(_ session: ARSession, didUpdate frame: ARFrame) {
}
func sessionWasInterrupted(_ session: ARSession) {
// Inform the user that the session has been interrupted, for example, by presenting an overlay
}
func sessionInterruptionEnded(_ session: ARSession) {
// Reset tracking and/or remove existing anchors if consistent tracking is required
}
}