我一直试图将Apple的MetalBasicTessellation项目转换为在iPad Air 3上的swift 3中工作，但到目前为止还没有成功。令人沮丧的是，该项目带有iOS实现（用ObjectiveC编写，并且是一个快速的游乐场），但没有快速实现。
我已经获得了编译代码，但无法在我的iPad上运行，并出现以下错误：
2017-05-14 14:25:54.268400-0700 MetalBasicTessellation[2436:570250] -[MTLRenderPipelineDescriptorInternal validateWithDevice:], line 1728: error 'tessellation is only supported on MTLFeatureSet_iOS_GPUFamily3_v1 and later'
我很确定iPad Air 2是合规的，但我觉得错误是由于MetalKitView配置不当造成的。我已经从项目的objective-c和playground文件中进行了逆向工程，但是我已经能够理解我目前的专业知识。
//
// ViewController.swift
// MetalBasicTessellation
//
// Created by vladimir sierra on 5/10/17.
//
//
import UIKit
import Metal
import MetalKit
class ViewController: UIViewController {
@IBOutlet weak var mtkView: MTKView!
// Seven steps required to set up metal for rendering:
// 1. Create a MTLDevice
// 2. Create a CAMetalLayer
// 3. Create a Vertex Buffer
// 4. Create a Vertex Shader
// 5. Create a Fragment Shader
// 6. Create a Render Pipeline
// 7. Create a Command Queue
var device: MTLDevice! // to be initialized in viewDidLoad
//var metalLayer: CAMetalLayer! // to be initialized in viewDidLoad
var vertexBuffer: MTLBuffer! // to be initialized in viewDidLoad
var library: MTLLibrary!
// once we create a vertex and fragment shader, we combine them in an object called render pipeline. In Metal the shaders are precompiled, and the render pipeline configuration is compiled after you first set it up. This makes everything extremely efficient
var renderPipeline: MTLRenderPipelineState! // to be initialized in viewDidLoad
var commandQueue: MTLCommandQueue! // to be initialized in viewDidLoad
//var timer: CADisplayLink! // function to be called every time the device screen refreshes so we can redraw the screen
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
/*
if let window = view.window {
let scale = window.screen.nativeScale // (2 for iPhone 5s, 6 and iPads; 3 for iPhone 6 Plus)
let layerSize = view.bounds.size
// apply the scale to increase the drawable texture size.
view.contentScaleFactor = scale
//metalLayer.frame = CGRect(x: 0, y: 0, width: layerSize.width, height: layerSize.height)
//metalLayer.drawableSize = CGSize(width: layerSize.width * scale, height: layerSize.height * scale)
} */
}
override func viewDidLoad() {
super.viewDidLoad()
device = MTLCreateSystemDefaultDevice() // returns a reference to the default MTLDevice
//device.supportsFeatureSet(MTLFeatureSet_iOS_GPUFamily3_v2)
// set up layer to display metal content
//metalLayer = CAMetalLayer() // initialize metalLayer
//metalLayer.device = device // device the layer should use
//metalLayer.pixelFormat = .bgra8Unorm // normalized 8 bit rgba
//metalLayer.framebufferOnly = true // set to true for performance issues
//view.layer.addSublayer(metalLayer) // add sublayer to main view's layer
// precompile custom metal functions
let defaultLibrary = device.newDefaultLibrary()! // MTLLibrary object with precompiled shaders
let fragmentProgram = defaultLibrary.makeFunction(name: "tessellation_fragment")
let vertexProgram = defaultLibrary.makeFunction(name: "tessellation_vertex_triangle")
// Setup Compute Pipeline
let kernelFunction = defaultLibrary.makeFunction(name: "tessellation_kernel_triangle")
var computePipeline: MTLComputePipelineState?
do {
computePipeline = try device.makeComputePipelineState(function: kernelFunction!)
} catch let error as NSError {
print("compute pipeline error: " + error.description)
}
// Setup Vertex Descriptor
let vertexDescriptor = MTLVertexDescriptor()
vertexDescriptor.attributes[0].format = .float4
vertexDescriptor.attributes[0].offset = 0
vertexDescriptor.attributes[0].bufferIndex = 0;
vertexDescriptor.layouts[0].stepFunction = .perPatchControlPoint
vertexDescriptor.layouts[0].stepRate = 1
vertexDescriptor.layouts[0].stride = 4*MemoryLayout<Float>.size
// Setup Render Pipeline
let renderPipelineDescriptor = MTLRenderPipelineDescriptor()
renderPipelineDescriptor.vertexDescriptor = vertexDescriptor
//renderPipelineDescriptor.fragmentFunction = defaultLibrary.makeFunction(name: "tessellation_fragment")
renderPipelineDescriptor.fragmentFunction = fragmentProgram
//renderPipelineDescriptor.vertexFunction = defaultLibrary.makeFunction(name: "tessellation_vertex_triangle")
renderPipelineDescriptor.vertexFunction = vertexProgram
//renderPipelineDescriptor.colorAttachments[0].pixelFormat = .bgra8Unorm // normalized 8 bit rgba
renderPipelineDescriptor.colorAttachments[0].pixelFormat = mtkView.colorPixelFormat
renderPipelineDescriptor.isTessellationFactorScaleEnabled = false
renderPipelineDescriptor.tessellationFactorFormat = .half
renderPipelineDescriptor.tessellationControlPointIndexType = .none
renderPipelineDescriptor.tessellationFactorStepFunction = .constant
renderPipelineDescriptor.tessellationOutputWindingOrder = .clockwise
renderPipelineDescriptor.tessellationPartitionMode = .fractionalEven
renderPipelineDescriptor.maxTessellationFactor = 64;
// Compile renderPipeline
do {
renderPipeline = try device.makeRenderPipelineState(descriptor: renderPipelineDescriptor)
} catch let error as NSError {
print("render pipeline error: " + error.description)
}
// Setup Buffers
let tessellationFactorsBuffer = device.makeBuffer(length: 256, options: MTLResourceOptions.storageModePrivate)
let controlPointPositions: [Float] = [
-0.8, -0.8, 0.0, 1.0, // lower-left
0.0, 0.8, 0.0, 1.0, // upper-middle
0.8, -0.8, 0.0, 1.0, // lower-right
]
let controlPointsBuffer = device.makeBuffer(bytes: controlPointPositions, length:256 , options: [])
// Tessellation Pass
let commandBuffer = commandQueue.makeCommandBuffer()
let computeCommandEncoder = commandBuffer.makeComputeCommandEncoder()
computeCommandEncoder.setComputePipelineState(computePipeline!)
let edgeFactor: [Float] = [16.0]
let insideFactor: [Float] = [8.0]
computeCommandEncoder.setBytes(edgeFactor, length: MemoryLayout<Float>.size, at: 0)
computeCommandEncoder.setBytes(insideFactor, length: MemoryLayout<Float>.size, at: 1)
computeCommandEncoder.setBuffer(tessellationFactorsBuffer, offset: 0, at: 2)
computeCommandEncoder.dispatchThreadgroups(MTLSizeMake(1, 1, 1), threadsPerThreadgroup: MTLSizeMake(1, 1, 1))
computeCommandEncoder.endEncoding()
let renderPassDescriptor = mtkView.currentRenderPassDescriptor
let renderCommandEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: renderPassDescriptor!)
renderCommandEncoder.setRenderPipelineState(renderPipeline!)
renderCommandEncoder.setVertexBuffer(controlPointsBuffer, offset: 0, at: 0)
renderCommandEncoder.setTriangleFillMode(.lines)
renderCommandEncoder.setTessellationFactorBuffer(tessellationFactorsBuffer, offset: 0, instanceStride: 0)
renderCommandEncoder.drawPatches(numberOfPatchControlPoints: 3, patchStart: 0, patchCount: 1, patchIndexBuffer: nil, patchIndexBufferOffset: 0, instanceCount: 1, baseInstance: 0)
renderCommandEncoder.endEncoding()
commandBuffer.present(mtkView.currentDrawable!)
commandBuffer.commit()
commandBuffer.waitUntilCompleted()
/*
// finally create an ordered list of commands forthe GPU to execute
commandQueue = device.makeCommandQueue()
timer = CADisplayLink(target: self, selector: #selector(ViewController.gameloop)) // call gameloop every time the screen refreshes
timer.add(to: RunLoop.main, forMode: RunLoopMode.defaultRunLoopMode)
*/
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
/*
func render() {
guard let drawable = metalLayer?.nextDrawable() else { return } // returns the texture to draw into in order for something to appear on the screen
//objectToDraw.render(commandQueue: commandQueue, renderPipeline: renderPipeline, drawable: drawable, clearColor: nil)
}
// this is the routine that gets run every time the screen refreshes
func gameloop() {
autoreleasepool {
self.render()
}
} */
}
可以找到整个git here
某种金属大师灵魂会伸出援手吗？那里的文档很少。
答案 0 :(得分：4)
docs for MTLFeatureSet_iOS_GPUFamily3_v1说：
推出 Apple A9 GPU 和iOS 9.0。
（强调补充。）
同时，iOS Device Compatibility Reference: Hardware GPU Information文章称iPad Air 2具有 A8 GPU。
我不相信你的设备有能力。
通常，MTKView的配置不会影响所支持的功能集。这是设备中固有的（硬件和操作系统版本的组合）。您可以使用supportsFeatureSet(_:) method of MTLDevice查询设备是否支持给定的功能集。由于设备可以（并且通常是）独立于任何其他对象（例如MTKView）获取，因此功能集支持不依赖于此类其他对象。