CAMetalLayer transparency

Hi there!

I am trying to render CAMetalLayer with transparent background and i am facing these issues:

1) Transparency can only be achieved with renderPassDescriptor.colorAttachments[0].clearColor = MTLClearColor().

Other colors with alpha, event MTLClearColor(red: 1, green: 1, blue: 1, alpha: 0) not makes layer transparent.

(isOpaque = false, renderPassDescriptor.colorAttachments[0].loadAction = .clear -- used)

2)When I'm setting isOpaque to false: very strange color blending begins, dont know how to describe it, but I have triangles with alpha from 1 to 0 on the edges for antialiasing, and blending on this edges (when one figure intersects with other) is not right, though I have blending setting like this:

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

, and when i turn isOpaque to on everything goes well.

What am I missing?

Thanks.