Question

我正在尝试用Metal编写片段着色器，但无法理解如何传递单个值（例如float，float4或half4）。我的着色器如下：

#include <metal_stdlib>
using namespace metal;

typedef struct {
    float4 renderedCoordinate [[position]];
} FullscreenQuadVertex;

vertex FullscreenQuadVertex fullscreenQuad(unsigned int vertex_id [[ vertex_id ]]) {
    float4x4 renderedCoordinates = float4x4(float4( -1.0, -1.0, 0.0, 1.0 ),
                                            float4(  1.0, -1.0, 0.0, 1.0 ),
                                            float4( -1.0,  1.0, 0.0, 1.0 ),
                                            float4(  1.0,  1.0, 0.0, 1.0 ));

    FullscreenQuadVertex outVertex;
    outVertex.renderedCoordinate = renderedCoordinates[vertex_id];

    return outVertex;
}

fragment float4 displayColor(device float4 *color [[ buffer(0) ]]) {
//    return float4(0.2, 0.5, 0.8, 1);
    return *color;
}

我从这样的MTKView子类传递颜色：

import MetalKit

class MetalView: MTKView {

    var color = NSColor(deviceRed: 0.2, green: 0.4, blue: 0.8, alpha: 1)
    var pipeline: MTLRenderPipelineState!
    var colorBuffer: MTLBuffer!

    init() {
        super.init(frame: CGRect.zero, device: nil)
        setup()
    }

    required init(coder: NSCoder) {
        super.init(coder: coder)
        setup()
    }

    func setup() {
        device = MTLCreateSystemDefaultDevice()
        colorPixelFormat = .bgra8Unorm

        // setup render pipeline for displaying the off screen buffer
        guard let library = device?.makeDefaultLibrary() else {
            fatalError("Failed to make Metal library")
        }

        let pipelineDescriptor = MTLRenderPipelineDescriptor()
        pipelineDescriptor.colorAttachments[0].pixelFormat = .bgra8Unorm
        pipelineDescriptor.colorAttachments[0].isBlendingEnabled = false
        pipelineDescriptor.vertexFunction = library.makeFunction(name: "fullscreenQuad")
        pipelineDescriptor.fragmentFunction = library.makeFunction(name: "displayColor")

        do {
            pipeline = try device?.makeRenderPipelineState(descriptor: pipelineDescriptor)
        } catch {
            fatalError("Failed to make render pipeline state")
        }

        colorBuffer = device?.makeBuffer(length: MemoryLayout<float4>.stride, options: .storageModeManaged)
        updateBackgroundColor()
    }

    func updateBackgroundColor() {
        var colorArray = [color.blueComponent, color.greenComponent, color.redComponent, color.alphaComponent].map { Float($0) }
        var data = Data(buffer: UnsafeBufferPointer(start: &colorArray, count: colorArray.count))

        colorBuffer.contents().copyMemory(from: &data, byteCount: data.count)
        colorBuffer.didModifyRange(0..<data.count)
    }

    override func draw(_ dirtyRect: NSRect) {
        drawColor()
    }

    func drawColor() {
        guard let commandQueue = device?.makeCommandQueue() else { return }
        guard let commandBuffer = commandQueue.makeCommandBuffer() else { return }
        guard let renderPassDescriptor = currentRenderPassDescriptor else { return }
        guard let currentDrawable = currentDrawable else { return }

        guard let commandEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: renderPassDescriptor) else { return }

        commandEncoder.setRenderPipelineState(pipeline)
        commandEncoder.setFragmentBuffer(colorBuffer, offset: 0, index: 0)
        commandEncoder.drawPrimitives(type: .triangleStrip, vertexStart: 0, vertexCount: 4)
        commandEncoder.endEncoding()

        commandBuffer.present(currentDrawable)
        commandBuffer.commit()
    }

}

尽管传入了我希望是蓝色的阴影，但我看到的只是黑色。测试从片段着色器返回的硬编码颜色效果很好。

我不是最流利的使用UnsafePointers和Data类型，因此不确定是设置缓冲区数据还是我实际上尝试将缓冲区数据传递到着色器的方式。我确实尝试了[[color（0）]]属性类型的着色器，但是据我所知，macOS不支持这些着色器（或者我做错了‍♂️）。

Answer 1

为什么不仅使用setFragmentBytes()直接发送颜色，而不是使用单色的缓冲区？这是它的外观：

var fragmentColor = vector_float4(Float(color.redComponent), Float(color.greenComponent), Float(color.blueComponent), Float(color.alphaComponent))
commandEncoder.setFragmentBytes(&fragmentColor, length: MemoryLayout.size(ofValue: fragmentColor), index: 0)

您的着色器仍将使用：

fragment float4 displayColor(constant float4 &color [[ buffer(0) ]])

将浮动或颜色传递到Swift的Metal片段着色器中

1 个答案: