Question

我在opengl中做了如下蒙版

vec4 patCol = texture2D(pattern, samplePos);
vec4 maskCol = texture2D(tex0, texCoordVarying);
gl_FragColor=vec4(patCol.xyz, patCol.w);

我想在iOS中进行相同的遮罩，maskCol中的纹理是半透明的。当我无法在Metal中获得类似的输出时。有人可以帮我吗？

渲染管线描述符

let pipelineDescriptor = MTLRenderPipelineDescriptor()
pipelineDescriptor.fragmentFunction = fragmentFunction
pipelineDescriptor.vertexFunction = vertexFunction
pipelineDescriptor.colorAttachments[0].pixelFormat = .bgra8Unorm
pipelineDescriptor.sampleCount = 1
pipelineDescriptor.colorAttachments[0].isBlendingEnabled = true
pipelineDescriptor.colorAttachments[0].rgbBlendOperation = .add
pipelineDescriptor.colorAttachments[0].alphaBlendOperation = .add
pipelineDescriptor.colorAttachments[0].sourceRGBBlendFactor = .one
pipelineDescriptor.colorAttachments[0].sourceAlphaBlendFactor = .one
pipelineDescriptor.colorAttachments[0].destinationRGBBlendFactor = .oneMinusSourceAlpha
pipelineDescriptor.colorAttachments[0].destinationAlphaBlendFactor = .oneMinusSourceAlpha

Answer 1

鉴于您未在退货中使用maskCol，我假设您正在尝试执行以下操作：

    float4 patCol...
    float4 maskCol...
    return float4(patCol.rgb, maskCol.a);

也就是说，从蒙版中获取alpha值并将其应用于源patCol ...

要使其正常工作，您需要在pipelineDescriptor中设置混合选项：

    pipelineDescriptor.colorAttachments[0].isBlendingEnabled = true
    pipelineDescriptor.colorAttachments[0].rgbBlendOperation = .add
    pipelineDescriptor.colorAttachments[0].alphaBlendOperation = .add
    pipelineDescriptor.colorAttachments[0].sourceRGBBlendFactor = .sourceAlpha
    pipelineDescriptor.colorAttachments[0].sourceAlphaBlendFactor = .sourceAlpha
    pipelineDescriptor.colorAttachments[0].destinationRGBBlendFactor = .oneMinusSourceAlpha
    pipelineDescriptor.colorAttachments[0].destinationAlphaBlendFactor = .oneMinusSourceAlpha

这将为您提供“默认”行为，即源混合，即：source.rgba + destination.rgba

Metal iOS中的遮罩

1 个答案: