如何为纹理渲染 iOS 应用程序启用 MSAA

Question

我有一个工作渲染纹理玩具 iOS 应用程序。问题是它有很多锯齿，因为它是点采样而不是抗锯齿：

我将 MTKView 子类中的样本数增加到 4 以启用 MSAA。

这是相关代码的样子。

// render to texture render pass descriptor
renderPassDesc = MTLRenderPassDescriptor()
renderPassDesc.EI_configure(clearColor: MTLClearColorMake(1, 1, 1, 1), clearDepth: 1)

// my MTLRenderPassDescriptor extension convenience method
public func EI_configure(clearColor:MTLClearColor, clearDepth: Double) {

    // color
    colorAttachments[ 0 ] = MTLRenderPassColorAttachmentDescriptor()
    colorAttachments[ 0 ].storeAction = .store
    colorAttachments[ 0 ].loadAction = .clear
    colorAttachments[ 0 ].clearColor = clearColor

    // depth
    depthAttachment = MTLRenderPassDepthAttachmentDescriptor()
    depthAttachment.storeAction = .dontCare
    depthAttachment.loadAction = .clear
    depthAttachment.clearDepth = clearDepth;

}

我将为 MSAA 配置的颜色和深度缓冲区附加到 renderPassDesc:

// color
let colorDesc = MTLTextureDescriptor.texture2DDescriptor(pixelFormat:view.colorPixelFormat, width:Int(view.bounds.size.width), height:Int(view.bounds.size.height), mipmapped:false)
colorDesc.mipmapLevelCount = 1;
colorDesc.textureType = .type2DMultisample
colorDesc.sampleCount = view.sampleCount
colorDesc.usage = [.renderTarget, .shaderRead]
renderPassDesc.colorAttachments[ 0 ].texture = view.device!.makeTexture(descriptor:colorDesc)

// depth
let depthDesc = MTLTextureDescriptor.texture2DDescriptor(pixelFormat:.depth32Float, width:Int(view.bounds.size.width), height:Int(view.bounds.size.height), mipmapped:false)
depthDesc.mipmapLevelCount = 1;
depthDesc.textureType = .type2DMultisample
depthDesc.sampleCount = view.sampleCount
depthDesc.usage = .renderTarget
renderPassDesc.depthAttachment.texture = view.device!.makeTexture(descriptor:depthDesc)

在我的绘制循环中，我的片段着色器使用渲染到的纹理时出现以下错误：

断言片段函数失败（finalPassOverlayFragmentShader）： underlay[0]

的索引 0 处的纹理绑定（预计 MTLTextureType2D）绑定的纹理类型不正确 (MTLTextureType2DMultisample)

这是片段着色器：

fragment float4 finalPassOverlayFragmentShader(InterpolatedVertex vert [[ stage_in ]],
                                               texture2d<float> underlay [[ texture(0) ]],
                                               texture2d<float> overlay [[ texture(1) ]]) {

    constexpr sampler defaultSampler;

    float4 _F = overlay.sample(defaultSampler, vert.st).rgba;

    float4 _B = underlay.sample(defaultSampler, vert.st).rgba;

    float4 rgba = _F + (1.0f - _F.a) * _B;

    return rgba;
}

我确定我在某处遗漏了一个设置，但我找不到它。

我错过了什么？

更新 0

我的 2-pass 玩具现在有 MSAA。唯一的问题是没有太多抗锯齿发生。事实上，很难说有什么改变。这是我的最新设置

// color - multi-sampled texture target
let desc = MTLTextureDescriptor.texture2DDescriptor(pixelFormat:format, width:w, height:h, mipmapped:false)
desc.mipmapLevelCount = 1;
desc.textureType = .type2DMultisample
desc.sampleCount = view.sampleCount
desc.usage = .renderTarget
let tex:MTLTexture? = view.device!.makeTexture(descriptor:desc)

// color - point-sampled resolve-texture
let resolveDesc = MTLTextureDescriptor.texture2DDescriptor(pixelFormat:format, width:w, height:h, mipmapped:true)
let resolveTex:MTLTexture? = view.device!.makeTexture(descriptor:resolveDesc)

// depth texture target
let depthDesc = MTLTextureDescriptor.texture2DDescriptor(pixelFormat:.format, width:w, height:h, mipmapped:false)
depthDesc.mipmapLevelCount = 1;
depthDesc.textureType = .type2DMultisample
depthDesc.sampleCount = view.sampleCount
depthDesc.usage = .renderTarget
let depthTex:MTLTexture? = view.device!.makeTexture(descriptor:depthDesc)

// render pass descriptor
renderPassDesc = MTLRenderPassDescriptor()
// color
renderPassDesc.colorAttachments[ 0 ] = MTLRenderPassColorAttachmentDescriptor()
renderPassDesc.colorAttachments[ 0 ].storeAction = .storeAndMultisampleResolve
renderPassDesc.colorAttachments[ 0 ].loadAction = .clear
renderPassDesc.colorAttachments[ 0 ].clearColor = MTLClearColorMake(0.25, 0.25, 0.25, 1)
renderPassDesc.colorAttachments[ 0 ].texture = tex
renderPassDesc.colorAttachments[ 0 ].resolveTexture = resolveTex
// depth
renderPassDesc.depthAttachment = MTLRenderPassDepthAttachmentDescriptor()
renderPassDesc.depthAttachment.storeAction = .dontCare
renderPassDesc.depthAttachment.loadAction = .clear
renderPassDesc.depthAttachment.clearDepth = 1;
renderPassDesc.depthAttachment.texture = depthTex

更新 1

锯齿似乎来自渲染到纹理，而不是在资产中。下面是并排比较。 top 图像是在启用 MSAA 的情况下使用单通道渲染的。 bottom 图像渲染为纹理。锯齿在底部图像中清晰可见

单程

2遍

Answer 1

错误与您的渲染目标无关（a.k.a。颜色和深度附件）。它与您通过渲染命令编码器的片段纹理 table 传递的纹理有关——也就是说，您调用的地方 setFragmentTexture(_:index:)。当着色器编码为预期 .type2D 时，您为索引 0 传递的是 .type2DMultisample，因为您将 underlay 声明为 texture2d<...>.

您的 MSAA 设置对于中间步骤是可行的。您最终需要将纹理解析为非多重采样纹理，以便将其绘制到屏幕上。对于该步骤（可能用于此渲染命令编码器或稍后的编码器，具体取决于您的需要），您需要将颜色附件的 storeAction 设置为 .multisampleResolve 或 .storeAndMultisampleResolve .并且您需要将 resolveTexture 设置为 2D 纹理。这可能是您自己的纹理或可绘制对象的纹理。

如何为纹理渲染 iOS 应用程序启用 MSAA

How Do I Enable MSAA for a Render to Texture iOS App

fragment-shader

msaa

swift

metal

metalkit

更新 0

更新 1