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我正在关注 Metal By Example 的 Metal 教程，并将代码转换为 Swift。

我正在运行第二个示例，由于某种原因，此代码不起作用。


import UIKit
import Metal
import MetalKit
import simd

class MBEMetalView: UIView {

     // // // // // MAIN // // // // //
     var metalDevice: MTLDevice! = nil
     var metalLayer: CAMetalLayer! = nil
     var commandQueue: MTLCommandQueue! = nil
     var vertexBuffer: MTLBuffer! = nil
     var pipelineState: MTLRenderPipelineState! = nil
     var displayLink: CADisplayLink! = nil

     override class var layerClass : AnyClass {
          return CAMetalLayer.self
     }
//     override func didMoveToWindow() {
//          self.redraw()
//     }
     override func didMoveToSuperview() {
          super.didMoveToSuperview()
          if self.superview != nil {
               self.displayLink = CADisplayLink(target: self, selector: #selector(displayLinkFired))
               self.displayLink.add(to: RunLoop.main, forMode: .common)
          } else {
               self.displayLink.invalidate()
          }
     }
     @objc func displayLinkFired() {
          self.redraw()
     }





     // // // // // INIT // // // // //
     required init?(coder aDecoder: NSCoder) {
          super.init(coder: aDecoder)
          self.prepareDeviceLayerAndQueue()
          self.makeBuffers()
          self.makePipeline()
     }

     func prepareDeviceLayerAndQueue() {
          metalLayer = (self.layer as! CAMetalLayer)
          metalDevice = MTLCreateSystemDefaultDevice()
          metalLayer.device = metalDevice
          metalLayer.pixelFormat = .bgra8Unorm
          commandQueue = metalDevice.makeCommandQueue()
     }

     func makeBuffers() {
          var vertices: [MBEVertex] = [
               MBEVertex(position: vector_float4(0, 0.5, 0, 1) , color: vector_float4(1, 0, 0, 1)),
               MBEVertex(position: vector_float4(-0.5, -0.5, 0, 1)  , color: vector_float4(0, 1, 0, 1)),
               MBEVertex(position: vector_float4(0.5, -0.5, 0, 1)  , color: vector_float4(0, 0, 1, 1))
          ]
          self.vertexBuffer = metalDevice.makeBuffer(bytes: &vertices, length: 56, options: .storageModeShared)
     }

     func makePipeline() {
          guard let library = metalDevice.makeDefaultLibrary() else { print("COULD NOT CREATE LIBRARY") ; return }
          guard let vertexFunction = library.makeFunction(name: "vertex_main") else { print("COULD NOT CREATE A VERTEX FUNCTION") ; return }
          guard let fragmentFunction = library.makeFunction(name: "fragment_main") else { print("COULD NOT CREATE LIBRARY") ; return }

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

          pipelineState = try? metalDevice.makeRenderPipelineState(descriptor: pipelineDescriptor)
          if pipelineState == nil { print("COULD NOT CREATE PIPELINE STATE") ; return }

     }





     // // // // // FUNCTIONS // // // // //
     func redraw() {
          guard let drawable = metalLayer.nextDrawable() else { print("COULD NOT CREATE A DRAWABLE") ; return }
          let texture = drawable.texture
          let renderPassDescriptor = MTLRenderPassDescriptor()
          renderPassDescriptor.colorAttachments[0].texture = texture
          renderPassDescriptor.colorAttachments[0].loadAction = .clear
          renderPassDescriptor.colorAttachments[0].storeAction = .store
          renderPassDescriptor.colorAttachments[0].clearColor = MTLClearColor(red: 0.1, green: 0.1, blue: 0.1, alpha: 1)

          guard let commandBuffer = commandQueue.makeCommandBuffer() else { print("COULD NOT CREATE A COMMAND BUFFER") ; return }
          guard let commandEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: renderPassDescriptor) else { print("COULD NOT CREATE AN ENCODER") ; return }

          commandEncoder.setRenderPipelineState(pipelineState)
          commandEncoder.setVertexBuffer(vertexBuffer, offset: 0, index: 0)
          commandEncoder.drawPrimitives(type: .triangle, vertexStart: 0, vertexCount: 3)

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





     // // // // // TYPES // // // // //
     struct MBEVertex {
          var position: vector_float4
          var color: vector_float4
     }

}

我很确定着色器不是问题，因为顶点着色器只是接收顶点缓冲区并返回顶点。

片段着色器只获取顶点着色器的输出和返回颜色。

视图控制器是默认的——没有碰过它。

我将控制器视图的类更改为这个 MBEMetalView 类。

我确实偶然发现了使用顶点指针、长度和“storageModeShared”选项创建顶点缓冲区的代码行出错。

最初，我将长度 = 设置为 MemoryLayout.size(of: vertices) 但根据控制台消息，当缓冲区需要长度为 32 时，仅创建长度为 8。

我只是增加了长度，错误就消失了......

但是，三角形是扭曲的，而不是正确的颜色。看起来前 2 个顶点的位置正确，但第三个顶点没有。

没有一个颜色是正确的。有任何想法吗？

当我更改缓冲区的长度时 - 三角形将改变形状或从屏幕上消失。

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1 回答 1

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无需猜测缓冲区的长度。您可以将其计算为顶点数乘以每个顶点占用的字节数：

let bufferLength = MemoryLayout<MBEVertex>.stride * vertices.count
self.vertexBuffer = metalDevice.makeBuffer(bytes: &vertices, length: bufferLength, options: .storageModeShared)

在这种情况下，结果实际上是 96。

这通常是比硬编码常量更好的方法。

于 2019-08-21T21:37:31.780 回答