Question

我正在尝试显示一个用MTKTextureLoader加载的纹理，我有一个存储顶点坐标的缓冲区（我构建了两个三角形，有一个矩形可以显示我的图像），然后我有一个存储纹理坐标的缓冲区每个顶点我做了一个采样器来从我的纹理中采样数据，问题是我什么都没得到（黑色图像）。

我推出了Swift代码以防我的错误来自那里，但我认为它来自Metal代码。如果您查看我的片段着色器，您会看到两条评论，它们会显示我无法理解的内容：

如果我将坐标直接提供给样本函数，它就可以工作（使用与给定坐标对应的颜色为三角形着色）。
如果我将作为颜色分量传递给采样器的坐标给出，它还会显示一些相干的东西（三角形颜色与给定坐标一致）。

所以它似乎不是来自采样器，也不是来自坐标，这是我不理解的。

这是我的Swift代码：

import Cocoa
import MetalKit
import Metal

class ViewController: NSViewController, MTKViewDelegate {

    var device:MTLDevice!
    var texture:MTLTexture!
    var commandQueue:MTLCommandQueue!
    var vertexBuffer:MTLBuffer!
    var vertexCoordinates:[Float] = [
        -1, 1, 0, 1,
        -1, -1, 0, 1,
        1, -1, 0,  1,

        1,-1,0,1,
        1,1,0,1,
        -1,1,0,1,

    ]

    var vertexUVBuffer:MTLBuffer!
    var vertexUVCoordinates:[Float] = [
    0,1,
    0,0,
    1,0,
    1,0,
    1,1,
    0,1
    ]

    var library:MTLLibrary!
    var defaultPipelineState:MTLRenderPipelineState!
    var samplerState:MTLSamplerState!

    @IBOutlet var metalView: MTKView!

    override func viewDidLoad() {
        super.viewDidLoad()

        device = MTLCreateSystemDefaultDevice()
        let textureLoader = MTKTextureLoader(device: device)

        metalView.device = device
        metalView.delegate = self
        metalView.preferredFramesPerSecond = 0
        metalView.sampleCount = 4



        texture = try! textureLoader.newTextureWithContentsOfURL(NSBundle.mainBundle().URLForResource("abeilles", withExtension: "jpg")!, options: [MTKTextureLoaderOptionAllocateMipmaps:NSNumber(bool: true)])

        commandQueue = device.newCommandQueue()
        library = device.newDefaultLibrary()


        vertexBuffer = device.newBufferWithBytes(&vertexCoordinates, length: sizeof(Float)*vertexCoordinates.count, options: [])
        vertexUVBuffer = device.newBufferWithBytes(&vertexUVCoordinates, length: sizeof(Float)*vertexUVCoordinates.count, options: [])



        let renderPipelineDescriptor = MTLRenderPipelineDescriptor()
        renderPipelineDescriptor.vertexFunction = library.newFunctionWithName("passTroughVertex")
        renderPipelineDescriptor.fragmentFunction = library.newFunctionWithName("myFragmentShader")
        renderPipelineDescriptor.sampleCount = metalView.sampleCount
        renderPipelineDescriptor.colorAttachments[0].pixelFormat = metalView.colorPixelFormat
        defaultPipelineState = try! device.newRenderPipelineStateWithDescriptor(renderPipelineDescriptor)
        let samplerDescriptor = MTLSamplerDescriptor()
        samplerDescriptor.minFilter = .Linear
        samplerDescriptor.magFilter = .Linear
        samplerDescriptor.mipFilter = .Linear
        samplerDescriptor.sAddressMode = .ClampToEdge
        samplerDescriptor.rAddressMode = .ClampToEdge
        samplerDescriptor.tAddressMode = .ClampToEdge
        samplerDescriptor.normalizedCoordinates = true

        samplerState = device.newSamplerStateWithDescriptor(samplerDescriptor)
        metalView.draw()






        // Do any additional setup after loading the view.
    }

    func drawInMTKView(view: MTKView) {

        let commandBuffer = commandQueue.commandBuffer()
        let commandEncoder = commandBuffer.renderCommandEncoderWithDescriptor(metalView.currentRenderPassDescriptor!)
        commandEncoder.setRenderPipelineState(defaultPipelineState)

        commandEncoder.setVertexBuffer(vertexBuffer, offset: 0, atIndex: 0)
        commandEncoder.setVertexBuffer(vertexUVBuffer, offset:0, atIndex:1)
        commandEncoder.setFragmentSamplerState(samplerState, atIndex: 0)
        commandEncoder.setFragmentTexture(texture, atIndex: 0)
        commandEncoder.drawPrimitives(MTLPrimitiveType.Triangle, vertexStart: 0, vertexCount: 6, instanceCount: 1)

        commandEncoder.endEncoding()
        commandBuffer.presentDrawable(metalView.currentDrawable!)
        commandBuffer.commit()

    }

    func mtkView(view: MTKView, drawableSizeWillChange size: CGSize) {
        // view.draw()
    }

    override var representedObject: AnyObject? {
        didSet {
        // Update the view, if already loaded.
        }
    }


}

这是我的金属代码：

#include <metal_stdlib>
using namespace metal;


struct VertexOut {
    float4 position [[position]];
    float2 texCoord;
};


vertex VertexOut passTroughVertex(uint vid [[ vertex_id]],
                                  constant float4 *vertexPosition [[ buffer(0) ]],
                                  constant float2 *vertexUVPos [[ buffer(1)]]) {

    VertexOut vertexOut;
    vertexOut.position = vertexPosition[vid];
    vertexOut.texCoord = vertexUVPos[vid];
    return vertexOut;
}

fragment float4 myFragmentShader(VertexOut inFrag [[stage_in]],
                                 texture2d<float> myTexture [[ texture(0)]],
                                 sampler mySampler [[ sampler(0) ]]) {


    float4 myColor = myTexture.sample(mySampler,inFrag.texCoord);
    // myColor = myTexture.sample(mySampler,float2(1));
    // myColor = float4(inFrag.texCoord.r,inFrag.texCoord.g,0,1);

    return myColor;
}

Answer 1

您为mipmap分配空间，但实际上并未生成它们。 The docs say在指定MTKTextureLoaderOptionAllocateMipmaps时，“在加载纹理时为纹理分配了一整套mipmap级别，并且您有责任生成mipmap内容。”

只要纹理相对于屏幕上的矩形较小，您的采样器配置会导致在基本mipmap级别对结果纹理进行采样，但如果您输入较大的纹理，它会开始采样较小的级别。 mipmap stack，拾取全黑像素，然后将它们混合在一起，使图像变暗或使输出完全变黑。

在加载纹理后，您应该使用MTLBlitCommandEncoder上的-generateMipmapsForTexture:方法生成一组完整的mipmap。

无法使用采样器

1 个答案: