启用 Metal 验证时，IOS Metal Stencil Buffer 项目崩溃

Question

我正在尝试学习如何在 Metal IOS 中实现 Stencil Buffer。目前，无需 Metal Validation 即可正常工作。但一旦我打开 Metal Validations，项目就会崩溃。

这是我的代码:- Metal View :-

import MetalKit

class DrawingView: MTKView {

    //Renderer to handle all the rendering of the Drawing View
    public var renderer: Renderer!

    override init(frame frameRect: CGRect, device: MTLDevice?) {
        super.init(frame: frameRect, device: device)
        self.configDrawingView()
    }

    required init(coder: NSCoder) {
        super.init(coder: coder)
        self.configDrawingView()
    }

    private func configDrawingView() {
        //Setting system default GPU
        self.device = MTLCreateSystemDefaultDevice()
        //Setting pixel format for the view
        self.colorPixelFormat = MTLPixelFormat.bgra8Unorm
        //Setting clear color of the view. View will be cleared in every frame
        self.clearColor = MTLClearColorMake(1.0, 1.0, 1.0, 1.0)
        //Setting sample count of drawing textures
        self.sampleCount = 1
        //Setting prefered frame rate
        self.preferredFramesPerSecond = 120
        //Setting auto resizing of the drawable to false. If the value is true, the currentDrawable object’s texture, depthStencilTexture object, and multisampleColorTexture object automatically resize as the view resizes. If the value is false, drawableSize does not change and neither does the size of these objects.
        self.autoResizeDrawable = false

        //Stencil
        self.clearStencil = 0
        self.depthStencilPixelFormat = MTLPixelFormat.depth32Float_stencil8

        //Setting up Renderer
        self.renderer = Renderer(withDevice: self.device!)
        //Using renderer and the MTKView delegate. This will call draw method every frame
        self.delegate = renderer
    }

}

渲染器:-

import MetalKit

class Renderer: NSObject {

    //Device
    private var device: MTLDevice!

    //CommandQueue
    private var commandQueue: MTLCommandQueue!

    //Mirror Vertex
    private var paintData: [Vertex] = [
        Vertex(position: float4(-0.75, -0.75, 0, 1), color: float4(1.0, 1.0, 0.0, 1.0)),
        Vertex(position: float4(-0.75, 0.75, 0, 1), color: float4(1.0, 1.0, 0.0, 1.0)),
        Vertex(position: float4(0.75, 0.75, 0, 1), color: float4(1.0, 1.0, 0.0, 1.0)),
        Vertex(position: float4(0.75, -0.75, 0, 1), color: float4(1.0, 1.0, 0.0, 1.0))
    ]
    //Mirror Indices
    private var paintIndicies: [UInt32] = [0, 1, 2, 0, 2, 3]
    //Mirror Vertex Buffer
    private var paintVertexBuffer: MTLBuffer!
    //Mirror Index Buffer
    private var paintIndexBuffer: MTLBuffer!

    //Paint Vertex
    private var stencilData: [Vertex] = [
        Vertex(position: float4(-1, 0, 0, 1), color: float4(0.0, 0.0, 1.0, 1.0)),
        Vertex(position: float4(0, 1, 0, 1), color: float4(0.0, 0.0, 1.0, 1.0)),
        Vertex(position: float4(0, -1, 0, 1), color: float4(0.0, 0.0, 1.0, 1.0)),
        Vertex(position: float4(1, 0, 0, 1), color: float4(0.0, 0.0, 1.0, 1.0))
    ]
    //Paint indices
    private var stencilIndices: [UInt32] = [0, 1, 2, 2, 1, 3]
    //Paint Vertex Buffer
    private var stencilVertexBuffer: MTLBuffer!
    //Paint Index Buffer
    private var stencilIndexBuffer: MTLBuffer!

    //Depth Stencil State
    private var depthStencilState: MTLDepthStencilState!
    private var maskStencilState: MTLDepthStencilState!
    private var drawStencilState: MTLDepthStencilState!

    private var library: MTLLibrary!

    private var vertexFunction: MTLFunction!
    private var fragmentFunction: MTLFunction!
    private var stencilFragmentFunction: MTLFunction!

    private var pipelineState: MTLRenderPipelineState!
    private var stencilPipelineState: MTLRenderPipelineState!

    init(withDevice device: MTLDevice) {
        super.init()
        self.device = device
        self.configure()
    }

    private func configure() {
        self.commandQueue = self.device.makeCommandQueue()

        self.setupPipelines()
        self.setupDepthStencil()
        self.setupBuffers()
    }

    private func setupDepthStencil() {
        var depthStencilStateDescriptor: MTLDepthStencilDescriptor = MTLDepthStencilDescriptor()
        depthStencilStateDescriptor.depthCompareFunction = MTLCompareFunction.less
        depthStencilStateDescriptor.isDepthWriteEnabled = true

        self.depthStencilState = self.device.makeDepthStencilState(descriptor: depthStencilStateDescriptor)

        depthStencilStateDescriptor = MTLDepthStencilDescriptor()
        depthStencilStateDescriptor.depthCompareFunction = MTLCompareFunction.less

        var stencilDescriptor: MTLStencilDescriptor = MTLStencilDescriptor()
        stencilDescriptor.stencilCompareFunction = MTLCompareFunction.always
        stencilDescriptor.depthStencilPassOperation = MTLStencilOperation.replace
        depthStencilStateDescriptor.backFaceStencil = stencilDescriptor
        depthStencilStateDescriptor.frontFaceStencil = stencilDescriptor
        depthStencilStateDescriptor.isDepthWriteEnabled = false

        self.drawStencilState = self.device.makeDepthStencilState(descriptor: depthStencilStateDescriptor)

        depthStencilStateDescriptor = MTLDepthStencilDescriptor()
        depthStencilStateDescriptor.depthCompareFunction = MTLCompareFunction.less

        stencilDescriptor = MTLStencilDescriptor()
        stencilDescriptor.stencilCompareFunction = MTLCompareFunction.equal
        depthStencilStateDescriptor.frontFaceStencil = stencilDescriptor
        depthStencilStateDescriptor.backFaceStencil = stencilDescriptor
        depthStencilStateDescriptor.isDepthWriteEnabled = true

        self.maskStencilState = self.device.makeDepthStencilState(descriptor: depthStencilStateDescriptor)

    }

    private func setupPipelines() {
        self.library = self.device.makeDefaultLibrary()

        self.vertexFunction = self.library.makeFunction(name: "vertexShader")
        self.fragmentFunction = self.library.makeFunction(name: "fragmentShader")
        self.stencilFragmentFunction = self.library.makeFunction(name: "stencilFragmentShader")

        var renderPipelineDescriptor: MTLRenderPipelineDescriptor = MTLRenderPipelineDescriptor()
        renderPipelineDescriptor.vertexFunction = self.vertexFunction
        renderPipelineDescriptor.fragmentFunction = self.fragmentFunction
        renderPipelineDescriptor.colorAttachments[0].pixelFormat = MTLPixelFormat.bgra8Unorm
        renderPipelineDescriptor.depthAttachmentPixelFormat = MTLPixelFormat.depth32Float_stencil8
        renderPipelineDescriptor.stencilAttachmentPixelFormat = MTLPixelFormat.depth32Float_stencil8

        do {
            self.pipelineState = try self.device.makeRenderPipelineState(descriptor: renderPipelineDescriptor)
        } catch {
            print("\(error)")
        }

        var renderPipelineDescriptorNoDraw: MTLRenderPipelineDescriptor = MTLRenderPipelineDescriptor()
        renderPipelineDescriptorNoDraw.vertexFunction = self.vertexFunction
        renderPipelineDescriptorNoDraw.fragmentFunction = self.stencilFragmentFunction
        renderPipelineDescriptorNoDraw.depthAttachmentPixelFormat = MTLPixelFormat.depth32Float_stencil8
        renderPipelineDescriptorNoDraw.stencilAttachmentPixelFormat = MTLPixelFormat.depth32Float_stencil8
        renderPipelineDescriptorNoDraw.colorAttachments[0].pixelFormat = MTLPixelFormat.bgra8Unorm //Problem Here ---- (1)
        renderPipelineDescriptorNoDraw.colorAttachments[0].writeMask = []

        do {
            self.stencilPipelineState = try self.device.makeRenderPipelineState(descriptor: renderPipelineDescriptorNoDraw)
        } catch {
            print("\(error)")
        }
    }

    private func setupBuffers() {
        self.stencilVertexBuffer = self.device.makeBuffer(bytes: self.stencilData, length: MemoryLayout<Vertex>.stride * self.stencilData.count, options: [])
        self.stencilIndexBuffer = self.device.makeBuffer(bytes: self.stencilIndices, length: MemoryLayout<UInt32>.size * self.stencilIndices.count, options: [])

        self.paintVertexBuffer = self.device.makeBuffer(bytes: self.paintData, length: MemoryLayout<Vertex>.stride * self.paintData.count, options: [])
        self.paintIndexBuffer = self.device.makeBuffer(bytes: self.paintIndicies, length: MemoryLayout<UInt32>.size * self.paintIndicies.count, options: [])
    }

}

extension Renderer: MTKViewDelegate {
    func mtkView(_ view: MTKView, drawableSizeWillChange size: CGSize) {

    }

    func draw(in view: MTKView) {
        let buffer: MTLCommandBuffer = self.commandQueue.makeCommandBuffer()!


        let renderPassDescriptor = view.currentRenderPassDescriptor
        renderPassDescriptor!.colorAttachments[0].clearColor = MTLClearColorMake(1.0, 1.0, 1.0, 1.0)
        let encoderClear = buffer.makeRenderCommandEncoder(descriptor: renderPassDescriptor!)
        encoderClear!.endEncoding()

        let renderPassDescriptorOther = MTLRenderPassDescriptor()
        renderPassDescriptorOther.colorAttachments[0].loadAction = MTLLoadAction.load
        renderPassDescriptorOther.colorAttachments[0].storeAction = MTLStoreAction.store
        renderPassDescriptorOther.colorAttachments[0].texture = view.currentDrawable?.texture
        let commandEncoderOther = buffer.makeRenderCommandEncoder(descriptor: renderPassDescriptorOther)
        Plane(withDevice: self.device, sizeOf: float2(100, 100), andPlaneCenterTo: float2(100, 100), withColor: float4(1.0, 0.0, 0.0, 1.0)).render(commandEncoder: commandEncoderOther!)
        commandEncoderOther?.endEncoding()

        let renderPassDescriptorOther1 = MTLRenderPassDescriptor()
        renderPassDescriptorOther1.colorAttachments[0].loadAction = MTLLoadAction.load
        renderPassDescriptorOther1.colorAttachments[0].storeAction = MTLStoreAction.store
        renderPassDescriptorOther1.colorAttachments[0].texture = view.currentDrawable?.texture
        let encoder: MTLRenderCommandEncoder = buffer.makeRenderCommandEncoder(descriptor: renderPassDescriptorOther1)!

        //Stencil
        encoder.setRenderPipelineState(self.stencilPipelineState)
        encoder.setStencilReferenceValue(1)
        encoder.setDepthStencilState(self.drawStencilState)
        encoder.setVertexBuffer(self.stencilVertexBuffer, offset: 0, index: 0)
        encoder.drawIndexedPrimitives(type: MTLPrimitiveType.triangle, indexCount: self.stencilIndices.count, indexType: MTLIndexType.uint32, indexBuffer: self.stencilIndexBuffer, indexBufferOffset: 0)

        //Paint
        encoder.setRenderPipelineState(self.pipelineState)
        encoder.setDepthStencilState(self.maskStencilState)
        encoder.setVertexBuffer(self.paintVertexBuffer, offset: 0, index: 0)
        encoder.drawIndexedPrimitives(type: MTLPrimitiveType.triangle, indexCount: self.paintIndicies.count, indexType: MTLIndexType.uint32, indexBuffer: self.paintIndexBuffer, indexBufferOffset: 0)
        encoder.endEncoding()

        buffer.present(view.currentDrawable!)
        buffer.commit()
    }
}

这是我的着色器文件:-

#include <metal_stdlib>
using namespace metal;

struct Vertex {
    float4 position [[position]];
    float4 color;
};  

vertex Vertex vertexShader(const device Vertex *vertexArray [[buffer(0)]], unsigned int vid [[vertex_id]]) {
    return vertexArray[vid];
}

fragment float4 fragmentShader(Vertex interpolated [[stage_in]]) {
    return interpolated.color;
}

fragment float4 fragmentShader_stencil(Vertex v [[stage_in]])
{
    return float4(1, 1, 1, 0.0);
}

当我打开 Metal Validation 时，它给出了这个错误:-

[MTLDebugRenderCommandEncoder validateFramebufferWithRenderPipelineState:]:1236:
failed assertion `For depth attachment, the renderPipelineState pixelFormat 
must be MTLPixelFormatInvalid, as no texture is set.'

然后我将渲染器中的 (1) 像素格式更改为 MTLPixelFormat.inavlid 它给了我另一个错误:-

[MTLDebugRenderCommandEncoder validateFramebufferWithRenderPipelineState:]:1196: 
failed assertion `For color attachment 0, the render pipeline's pixelFormat 
(MTLPixelFormatInvalid) does not match the framebuffer's pixelFormat 
(MTLPixelFormatBGRA8Unorm).'

有办法解决这个问题吗？我希望启用 Metal 验证。禁用验证后，它可以正常工作。

Answer 1

由于您要手动创建渲染 channel 描述符，因此需要确保配置所有相关附件的纹理和加载/存储操作。

您已经指定您的MTKView它应该为您管理深度/模板纹理，并将渲染管道状态配置为期望深度/模板纹理，因此您需要提供这样的创建渲染 channel 描述符时的纹理:

renderPassDescriptorOther1.depthAttachment.loadAction = .clear
renderPassDescriptorOther1.depthAttachment.storeAction = .dontCare
renderPassDescriptorOther1.depthAttachment.texture = view.depthStencilTexture

renderPassDescriptorOther1.stencilAttachment.loadAction = .clear
renderPassDescriptorOther1.stencilAttachment.storeAction = .dontCare
renderPassDescriptorOther1.stencilAttachment.texture = view.depthStencilTexture

顺便说一句，我不明白在绘制之前运行单独的“清除” channel 的原因。看来您只需将 renderPassDescriptorOther 的颜色附件的 loadAction 设置为 .clear 即可。