金属makeComputeCommandEncoder断言失败

Question

我正在尝试设置和执行计算内核，并将其输出提交给MTKView进行绘制。但是我得到以下崩溃：

 -[MTLDebugCommandBuffer computeCommandEncoder]:889: failed assertion `encoding in progress'

以下代码有什么问题？使用同一commandBuffer是否不支持将计算着色器的输出馈送到渲染管道？

func computeKernel(_ texture:MTLTexture, commandBuffer:MTLCommandBuffer) {
    let computeEncoder = commandBuffer.makeComputeCommandEncoder()
    computeEncoder?.setComputePipelineState(computePipelineState!)

    computeEncoder?.setTexture(texture, index: 0)
    computeEncoder?.setTexture(texture, index: 1)
    computeEncoder?.dispatchThreadgroups(threadgroupCount, threadsPerThreadgroup: threadgroupSize)
    computeEncoder?.endEncoding()

    /*
    commandBuffer.commit()
    commandBuffer.waitUntilCompleted()
     */
}


   override func draw(_ rect: CGRect) {


    guard let drawable = currentDrawable,
        let currentRenderPassDescriptor = currentRenderPassDescriptor
     else {
            return
    }



    // Set up command buffer and encoder
    guard let commandQueue = commandQueue else {
        print("Failed to create Metal command queue")
        return
    }

    guard let commandBuffer = commandQueue.makeCommandBuffer() else {
        print("Failed to create Metal command buffer")
        return
    }

    guard let commandEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: currentRenderPassDescriptor) else {
        print("Failed to create Metal command encoder")
        return
    }


    commandEncoder.label = "Preview display"

    let texture = ... //Grab a Metal texture
    computeKernel(texture, commandBuffer: commandBuffer)
    commandEncoder.setRenderPipelineState(defaultRenderPipelineState!)


    commandEncoder.setFragmentTexture(texture, index: 0)
    commandEncoder.setVertexBytes(vertices, length: vertices.count * MemoryLayout<AAPLVertex>.stride, index: 0)
    commandEncoder.drawPrimitives(type: .triangleStrip, vertexStart: 0, vertexCount: 4)
    commandEncoder.endEncoding()

    commandBuffer.present(drawable) // Draw to the screen
    commandBuffer.commit()
}

Answer 1

您可以将计算和渲染工作编码到同一命令缓冲区中，但是当现有命令编码器正在编码时，您无法启动另一个命令编码器。在您的情况下，您创建渲染命令编码器，然后调用一个函数，该函数将创建计算命令编码器，而无需结束渲染命令编码器。相反，您应该调用自己的计算函数，然后创建并使用渲染命令编码器。