学习Metal: MetalKit

当我们获取了Metal的设备之后, 就可以开始做Metal的渲染了. 我们可以使用Core Animation提供的CAMetalLayer, 或者MetalKit提供的MTKView来显示渲染的结果.

MetalKit提供的MTKView更为方便快捷.

我们新建一个Xcode Playground, 02.MTKView.playground.

我们首先需要引入需要引用的库:

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import MetalKit
import PlaygroundSupport

我们再从MTKView派生一个MyMetalView, 并重写draw方法.

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class MyMetalView: MTKView {
    override func draw(_ dirtyRect: NSRect) {
        super.draw(dirtyRect)

        let renderPassDescriptor: MTLRenderPassDescriptor? = self.currentRenderPassDescriptor
        let drawable: CAMetalDrawable? = self.currentDrawable

        let bgColor: MTLClearColor = MTLClearColor(red: 0.3, green: 0.4, blue: 0.5, alpha: 1)
        renderPassDescriptor?.colorAttachments[0].clearColor = bgColor

        let command_queue: MTLCommandQueue? = self.device?.makeCommandQueue()

        let command_buffer: MTLCommandBuffer? = command_queue?.makeCommandBuffer()

        let command_encoder: MTLCommandEncoder? = command_buffer?.makeRenderCommandEncoder(descriptor: renderPassDescriptor!)
        command_encoder?.endEncoding()

        command_buffer?.present(drawable!)
        command_buffer?.commit()
    }
}

可以从上面的代码看到, 我们使用了MTLRenderPassDescriptor, CAMetalDrawable, MTLCommandQueue, MTLCommandBuffer, MTLCommandEncoder等类, 做了一次最基本的渲染.

接着我们调用MyMetalView, 并显示到Playground的Live View中.

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let rect = CGRect(x: 0, y: 0, width: 320, height: 480)
let device = MTLCreateSystemDefaultDevice()!

let view = MyMetalView(frame: rect, device: device)

PlaygroundPage.current.liveView = view

打开Live View, 就可以看到我们本地的渲染结果.

/upload/2018-07/001.MyMetalKit.png

同样源码托管在github: https://github.com/young40/LearnMetal . 欢迎star, 感谢!

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