我正在尝试将随机网格物体渲染到MTKView，只要设备允许这样做。几乎我发现的所有金属示例都显示了如何绘制一块几何体，缓冲区大小只定义一次（即固定的）：
let dataSize = vertexCount * MemoryLayout<VertexWithColor>.size // size of the vertex data in bytes
let vertexBuffer: MTLBuffer = device!.makeBuffer(bytes: verticesWithColorArray, length: dataSize, options: []) // create a new buffer on the GPU
目标是在给定点云输入的情况下最终生成网格。我已经设置绘图以通过点击触发，如下所示：
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
if let touch = touches.first {
let touchPoint = touch.location(in: view)
print ("...touch \(touchPoint)")
autoreleasepool {
delaunayView.setupTriangles()
delaunayView.renderTriangles()
}
}
}
只要我不经常点击，我就可以使用新的三角形刷新屏幕。但是，如果我点击太快（比如说双击），应用程序崩溃时会出现以下错误：
[CAMetalLayerDrawable texture] should not be called after presenting the drawable.
性能显然与绘制的三角形数量有关。除了让应用程序稳定运行外，同样重要的是问题，我怎样才能最好地利用GPU来尽可能多地推送三角形？（在目前的状态下，应用程序吸引了大约30,000个在iPad Air 2）上以3 fps的三角形。
速度和帧率的任何指针/陷阱都是最受欢迎的
可以找到整个项目here：
此外，以下是相关的更新金属类
import Metal
import MetalKit
import GameplayKit
protocol MTKViewDelaunayTriangulationDelegate: NSObjectProtocol{
func fpsUpdate (fps: Int)
}
class MTKViewDelaunayTriangulation: MTKView {
//var kernelFunction: MTLFunction!
var pipelineState: MTLComputePipelineState!
var defaultLibrary: MTLLibrary! = nil
var commandQueue: MTLCommandQueue! = nil
var renderPipeline: MTLRenderPipelineState!
var errorFlag:Bool = false
var verticesWithColorArray : [VertexWithColor]!
var vertexCount: Int
var verticesMemoryByteSize:Int
let fpsLabel = UILabel(frame: CGRect(x: 0, y: 0, width: 400, height: 20))
var frameCounter: Int = 0
var frameStartTime = CFAbsoluteTimeGetCurrent()
weak var MTKViewDelaunayTriangulationDelegate: MTKViewDelaunayTriangulationDelegate?
////////////////////
init(frame: CGRect) {
vertexCount = 100000
//verticesMemoryByteSize = vertexCount * MemoryLayout<VertexWithColor>.size
verticesMemoryByteSize = vertexCount * MemoryLayout<VertexWithColor>.stride // apple recommendation
super.init(frame: frame, device: MTLCreateSystemDefaultDevice())
setupMetal()
//setupTriangles()
//renderTriangles()
}
required init(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
/*
override func draw(_ rect: CGRect) {
step() // needed to update frame counter
autoreleasepool {
setupTriangles()
renderTriangles()
}
} */
func step() {
frameCounter += 1
if frameCounter == 100
{
let frametime = (CFAbsoluteTimeGetCurrent() - frameStartTime) / 100
MTKViewDelaunayTriangulationDelegate?.fpsUpdate(fps: Int(1 / frametime)) // let the delegate know of the frame update
print ("...frametime: \((Int(1/frametime)))")
frameStartTime = CFAbsoluteTimeGetCurrent() // reset start time
frameCounter = 0 // reset counter
}
}
func setupMetal(){
// Steps required to set up metal for rendering:
// 1. Create a MTLDevice
// 2. Create a Command Queue
// 3. Access the custom shader library
// 4. Compile shaders from library
// 5. Create a render pipeline
// 6. Set buffer size of objects to be drawn
// 7. Draw to pipeline through a renderCommandEncoder
// 1. Create a MTLDevice
guard let device = MTLCreateSystemDefaultDevice() else {
errorFlag = true
//particleLabDelegate?.particleLabMetalUnavailable()
return
}
// 2. Create a Command Queue
commandQueue = device.makeCommandQueue()
// 3. Access the custom shader library
defaultLibrary = device.newDefaultLibrary()
// 4. Compile shaders from library
let fragmentProgram = defaultLibrary.makeFunction(name: "basic_fragment")
let vertexProgram = defaultLibrary.makeFunction(name: "basic_vertex")
// 5a. Define render pipeline settings
let renderPipelineDescriptor = MTLRenderPipelineDescriptor()
renderPipelineDescriptor.vertexFunction = vertexProgram
renderPipelineDescriptor.sampleCount = self.sampleCount
renderPipelineDescriptor.colorAttachments[0].pixelFormat = self.colorPixelFormat
renderPipelineDescriptor.fragmentFunction = fragmentProgram
// 5b. Compile renderPipeline with above renderPipelineDescriptor
do {
renderPipeline = try device.makeRenderPipelineState(descriptor: renderPipelineDescriptor)
} catch let error as NSError {
print("render pipeline error: " + error.description)
}
// initialize counter variables
frameStartTime = CFAbsoluteTimeGetCurrent()
frameCounter = 0
} // end of setupMetal
/// Generate set of vertices for our triangulation to use
func generateVertices(_ size: CGSize, cellSize: CGFloat, variance: CGFloat = 0.75, seed: UInt64 = numericCast(arc4random())) -> [Vertex] {
// How many cells we're going to have on each axis (pad by 2 cells on each edge)
let cellsX = (size.width + 4 * cellSize) / cellSize
let cellsY = (size.height + 4 * cellSize) / cellSize
// figure out the bleed widths to center the grid
let bleedX = ((cellsX * cellSize) - size.width)/2
let bleedY = ((cellsY * cellSize) - size.height)/2
let _variance = cellSize * variance / 4
var points = [Vertex]()
let minX = -bleedX
let maxX = size.width + bleedX
let minY = -bleedY
let maxY = size.height + bleedY
let generator = GKLinearCongruentialRandomSource(seed: seed)
for i in stride(from: minX, to: maxX, by: cellSize) {
for j in stride(from: minY, to: maxY, by: cellSize) {
let x = i + cellSize/2 + CGFloat(generator.nextUniform()) + CGFloat.random(-_variance, _variance)
let y = j + cellSize/2 + CGFloat(generator.nextUniform()) + CGFloat.random(-_variance, _variance)
points.append(Vertex(x: Double(x), y: Double(y)))
}
}
return points
} // end of generateVertices
func setupTriangles(){
// generate n random triangles
///////////////////
verticesWithColorArray = [] // empty out vertex array
for _ in 0 ... vertexCount {
//for vertex in vertices {
let x = Float(Double.random(-1.0, 1.0))
let y = Float(Double.random(-1.0, 1.0))
let v = VertexWithColor(x: x, y: y, z: 0.0, r: Float(Double.random()), g: Float(Double.random()), b: Float(Double.random()), a: 0.0)
verticesWithColorArray.append(v)
} // end of for _ in
} // end of setupTriangles
func renderTriangles(){
// 6. Set buffer size of objects to be drawn
//let dataSize = vertexCount * MemoryLayout<VertexWithColor>.size // size of the vertex data in bytes
let dataSize = vertexCount * MemoryLayout<VertexWithColor>.stride // apple recommendation
let vertexBuffer: MTLBuffer = device!.makeBuffer(bytes: verticesWithColorArray, length: dataSize, options: []) // create a new buffer on the GPU
let renderPassDescriptor: MTLRenderPassDescriptor? = self.currentRenderPassDescriptor
// If the renderPassDescriptor is valid, begin the commands to render into its drawable
if renderPassDescriptor != nil {
// Create a new command buffer for each tessellation pass
let commandBuffer: MTLCommandBuffer? = commandQueue.makeCommandBuffer()
// Create a render command encoder
// 7a. Create a renderCommandEncoder four our renderPipeline
let renderCommandEncoder: MTLRenderCommandEncoder? = commandBuffer?.makeRenderCommandEncoder(descriptor: renderPassDescriptor!)
renderCommandEncoder?.label = "Render Command Encoder"
//////////renderCommandEncoder?.pushDebugGroup("Tessellate and Render")
renderCommandEncoder?.setRenderPipelineState(renderPipeline!)
renderCommandEncoder?.setVertexBuffer(vertexBuffer, offset: 0, at: 0)
// most important below: we tell the GPU to draw a set of triangles, based on the vertex buffer. Each triangle consists of three vertices, starting at index 0 inside the vertex buffer, and there are vertexCount/3 triangles total
//renderCommandEncoder?.drawPrimitives(type: .triangle, vertexStart: 0, vertexCount: vertexCount, instanceCount: vertexCount/3)
renderCommandEncoder?.drawPrimitives(type: .triangle, vertexStart: 0, vertexCount: vertexCount)
///////////renderCommandEncoder?.popDebugGroup()
renderCommandEncoder?.endEncoding() // finalize renderEncoder set up
commandBuffer?.present(self.currentDrawable!) // needed to make sure the new texture is presented as soon as the drawing completes
// 7b. Render to pipeline
commandBuffer?.commit() // commit and send task to gpu
} // end of if renderPassDescriptor
}// end of func renderTriangles()
} // end of class MTKViewDelaunayTriangulation
答案 0 :(得分：3)
您不应该从setupTriangles()致电renderTriangles()或特别是init()。根据你的评论，touchesBegan()也不是。通常，您只应在框架调用覆盖draw(_:)。
如何更新用户事件取决于MTKView的绘图模式，如课程概述中所述。默认情况下，会定期调用draw(_:)方法。在这种模式下，您不必对touchesBegan()中的绘图做任何事情。只需更新课程内部状态，了解应该绘制的内容。实际绘图将在不久后自动发生。
如果您已将视图配置为在setNeedsDisplay()之后重绘，则touchesBegan()应更新内部状态，然后调用setNeedsDisplay()。它不应该立即尝试绘制。将控制权返回到框架后的短时间内（即从touchesBegan()返回），它会为您调用draw(_:)。
如果您已将视图配置为仅在明确调用draw()时进行绘制，那么您将在更新内部状态后执行此操作。