金属程序崩溃

Question

import PlaygroundSupport
import MetalKit

guard let device = MTLCreateSystemDefaultDevice() else {
    fatalError("GPU is not supported")
}

let frame = CGRect(x: 0, y: 0, width: 600, height: 600)
let view = MTKView(frame: frame, device:device)
view.clearColor = MTLClearColor(red: 1, green: 1, blue: 0.8, alpha: 1)

//1
let allocator = MTKMeshBufferAllocator(device: device)
//2
let mdlMesh = MDLMesh(sphereWithExtent: [0.75, 0.75, 0.75], segments: [100, 100], inwardNormals: false, geometryType: .triangles, allocator: allocator)
//3
let mesh = try MTKMesh(mesh: mdlMesh, device: device)

guard let commandQueue = device.makeCommandQueue() else {
    fatalError("Could not create a command queue")
}

//shader
let shader = """
#include <metal_stdlib>

using namespace metal;

struct VertexIn {
    float4 position [[attribute(0)]];
};

vertex float4 vertex_main(const VertexIn vertex_in [[stage_in]])
{
    return vertex_in.position;
}

fragment float4 fragment_main() {
    return float4(1, 0, 0, 1);
}
"""

let library = try device.makeLibrary(source: shader, options: nil)
let vertexFunction = library.makeFunction(name: "vertex_main")
let fragmentFunction = library.makeFunction(name: "fragment_main")

//Pipeline

let pipelineDescriptor = MTLRenderPipelineDescriptor()
pipelineDescriptor.colorAttachments[0].pixelFormat = .bgra8Unorm
pipelineDescriptor.vertexFunction = vertexFunction
pipelineDescriptor.fragmentFunction = fragmentFunction

pipelineDescriptor.vertexDescriptor = MTKMetalVertexDescriptorFromModelIO(mesh.vertexDescriptor)

let pipelineState = try device.makeRenderPipelineState(descriptor: pipelineDescriptor)

// 1
guard let commandBuffer = commandQueue.makeCommandBuffer(),
      //2
      let renderPassDescriptor = view.currentRenderPassDescriptor,
      //3
      let renderEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: renderPassDescriptor)
else { fatalError() }

guard let submesh = mesh.submeshes.first else {
    fatalError()
}

//Here is where crashed.
renderEncoder.drawIndexedPrimitives(type: .triangle,
                  indexCount: submesh.indexCount,
                  indexType: submesh.indexType,
                  indexBuffer: submesh.indexBuffer.buffer,
                  indexBufferOffset: 0)

//1.u tell the render encoder that there are no more draw calls and end the render pass.
renderEncoder.endEncoding()

//2 u get the drawable from the MTKView.The MTKView is backed by a Core Animation CAMetalLayer and the layer owns a drawable texture which Metal can read and write to.
guard let drawable = view.currentDrawable else {
    fatalError()
}
//3.Ask the command Buffer to present the MTKVIew's drawable and commit to the GPU
commandBuffer.present(drawable)
commandBuffer.commit()

PlaygroundPage.current.liveView = view

错误：执行被中断，原因：EXC_BAD_ACCESS（代码=1，地址=0x220）。 进程一直停留在中断点，使用“thread return -x”返回到表达式求值前的state。

我在Xcode重新写了一遍，还是找不到问题出在哪里。

错误：执行被中断，原因：EXC_BAD_ACCESS（代码=1，地址=0x220）。 进程一直停留在中断点，使用“thread return -x”返回到表达式求值前的state。

我在Xcode重新写了一遍，还是找不到问题出在哪里。

错误：执行被中断，原因：EXC_BAD_ACCESS（代码=1，地址=0x220）。 进程一直停留在中断点，使用“thread return -x”返回到表达式求值前的state。

我在Xcode重新写了一遍，还是找不到问题出在哪里。

Answer 1

首先似乎有一些 XCode 错误，一旦您的代码崩溃不止一次，它会禁止提供有用的错误信息，您只需退出并重新启动它。

现在谈到主要问题，您错过了几件事：

1. 在命令编码器上设置渲染管道 state 以便您的着色器实际运行 GPU
2. 并将顶点缓冲区设置为命令编码器，以便 GPU 知道需要渲染网格的哪些点

我已经在下面更新了你的代码，而且，你不必每次都创建大部分对象，如管道、库、命令队列。 我假设你这样做只是因为它是一个游乐场。 我试图在下面的示例中向它添加一些基本结构，你可以在它的基础上构建，比如使用 MTKView delgates 等。

import UIKit
import PlaygroundSupport
import MetalKit

class BasicRenderer {
    var mesh: MTKMesh
    var pipelineState: MTLRenderPipelineState
    var device: MTLDevice
    var commandQueue: MTLCommandQueue
    
    var metalView: MTKView
    
    init() {
        
        guard let device = MTLCreateSystemDefaultDevice() else {
            fatalError("Can't create device")
        }
        self.device = device
        
        
        guard let commandQueue = device.makeCommandQueue() else {
            fatalError("Can't create commandQueue")
        }
        self.commandQueue = commandQueue
        
        
        metalView = MTKView(frame: .zero, device: device)
        metalView.clearColor = MTLClearColor(red: 1, green: 1, blue: 0.8, alpha: 1)
        
        
        let meshAllocator = MTKMeshBufferAllocator(device: device)
        let mdlMesh = MDLMesh(sphereWithExtent: [0.75, 0.75, 0.75],
                          segments: [100, 100],
                          inwardNormals: false,
                          geometryType: .triangles,
                          allocator: meshAllocator)
        guard let mesh = try? MTKMesh(mesh: mdlMesh, device: device) else {
            fatalError("Can't create mesh")
        }
        self.mesh = mesh
       
        
        let shader = """
            #include <metal_stdlib>

            using namespace metal;

            struct VertexIn {
                float4 position [[attribute(0)]];
            };

            vertex float4 vertex_main(const VertexIn vertex_in [[stage_in]])
            {
                return vertex_in.position;
            }

            fragment float4 fragment_main() {
                return float4(1, 0, 0, 1);
            }
        """
        
        guard let library = try? device.makeLibrary(source: shader, options: nil) else {
            fatalError("Can't create library")
        }
        
        let vertexFunction = library.makeFunction(name: "vertex_main")
        let fragmentFunction = library.makeFunction(name: "fragment_main")
        
        let pipelineDescriptor = MTLRenderPipelineDescriptor()
        pipelineDescriptor.colorAttachments[0].pixelFormat = .bgra8Unorm
        pipelineDescriptor.vertexFunction = vertexFunction
        pipelineDescriptor.fragmentFunction = fragmentFunction
        
        pipelineDescriptor.vertexDescriptor = MTKMetalVertexDescriptorFromModelIO(mesh.vertexDescriptor)
        
        guard let pipelineState = try? device.makeRenderPipelineState(descriptor: pipelineDescriptor) else {
            fatalError("Can't create pipelineState")
        }
        self.pipelineState = pipelineState
    }
    
    
    func render(in size: CGSize) {
        metalView.frame = CGRect(origin: .zero, size: size)
        
        guard let commandBuffer = commandQueue.makeCommandBuffer(),
              let renderPassDescriptor = metalView.currentRenderPassDescriptor,
              let renderEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: renderPassDescriptor)
        else {
            fatalError("Can't create commandBuffer/renderPassDescriptor/renderEncoder")
        }
        
        guard let subMesh = mesh.submeshes.first else {
            fatalError("Can't get submesh")
        }
        
        guard let vertexBuffer = mesh.vertexBuffers.first?.buffer else {
            fatalError("Can't get vertexBuffer")
        }
        
        // MARK: You missed setting pipeline state and vertex buffer on commandEncoder
        renderEncoder.setRenderPipelineState(pipelineState)
        renderEncoder.setVertexBuffer(vertexBuffer, offset: 0, index: 0)
        
        renderEncoder.drawIndexedPrimitives(type: .triangle,
                                            indexCount: subMesh.indexCount,
                                            indexType: subMesh.indexType,
                                            indexBuffer: subMesh.indexBuffer.buffer,
                                            indexBufferOffset: 0)
        
        renderEncoder.endEncoding()
        
        guard let drawable = metalView.currentDrawable else {
            fatalError("Can't get currentDrawable")
        }

        commandBuffer.present(drawable)
        commandBuffer.commit()
    }
}

class MyViewController : UIViewController {
   
   
    var basicRenderer = BasicRenderer()
    override func loadView() {
        self.view = basicRenderer.metalView
        basicRenderer.render(in: CGSize(width: 600, height: 600))
        
    }
}

PlaygroundPage.current.liveView = MyViewController()