swift - MetalKit - Drawable.texture 断言错误

Question

我是 MetalKit 的新手，正在尝试转换 this tutorial从 playground 回到 OSX app:

    import MetalKit

public class MetalView: MTKView {

    var queue: MTLCommandQueue! = nil
    var cps: MTLComputePipelineState! = nil

    required public init(coder: NSCoder) {
        super.init(coder: coder)
        device = MTLCreateSystemDefaultDevice()
        registerShaders()
    }


    override public func drawRect(dirtyRect: NSRect) {
        super.drawRect(dirtyRect)
        if let drawable = currentDrawable {
            let command_buffer = queue.commandBuffer()
            let command_encoder = command_buffer.computeCommandEncoder()
            command_encoder.setComputePipelineState(cps)
            command_encoder.setTexture(drawable.texture, atIndex: 0)
            let threadGroupCount = MTLSizeMake(8, 8, 1)
            let threadGroups = MTLSizeMake(drawable.texture.width / threadGroupCount.width, drawable.texture.height / threadGroupCount.height, 1)
            command_encoder.dispatchThreadgroups(threadGroups, threadsPerThreadgroup: threadGroupCount)
            command_encoder.endEncoding()
            command_buffer.presentDrawable(drawable)
            command_buffer.commit()
        }
    }

    func registerShaders() {
        queue = device!.newCommandQueue()
        do {
            let library = device!.newDefaultLibrary()!
            let kernel = library.newFunctionWithName("compute")!
            cps = try device!.newComputePipelineStateWithFunction(kernel)
        } catch let e {
            Swift.print("\(e)")
        }
    }
}

我在行中遇到错误:

command_encoder.setTexture(drawable.texture, atIndex: 0)

failed assertion `frameBufferOnly texture not supported for compute.'

我该如何解决这个问题？

Answer 1

如果你想从一个计算函数写入一个可绘制对象的纹理，你需要告诉 MTKView 它应该配置它的层而不是 framebuffer-only:

metalView.framebufferOnly = false

将此值设置为 false，您的可绘制对象将为您提供设置了 shaderWrite 使用标志的纹理，这是从着色器函数写入纹理时所必需的。