How to enable/disable DepthMask in Metal iOS

Question

I am trying to use Metal to display some 3D objects with complex alpha.

I am getting white edge in same object to object alpha blending. But in different object is working fine.

I had solved this issue in Android by disabling depthMask within one object.

Can anyone help me how to do it in Metal iOS?

My renderEncoder is as follows:

let pipelineStateDescriptor = MTLRenderPipelineDescriptor()
        pipelineStateDescriptor.vertexFunction = vertexProgram
        pipelineStateDescriptor.fragmentFunction = fragmentProgram
        pipelineStateDescriptor.colorAttachments[0].pixelFormat = .BGRA8Unorm
        pipelineStateDescriptor.colorAttachments[0].blendingEnabled = true
        pipelineStateDescriptor.colorAttachments[0].rgbBlendOperation = MTLBlendOperation.Add;
        pipelineStateDescriptor.colorAttachments[0].alphaBlendOperation = MTLBlendOperation.Add;
        pipelineStateDescriptor.colorAttachments[0].sourceRGBBlendFactor = MTLBlendFactor.SourceAlpha;
        pipelineStateDescriptor.colorAttachments[0].sourceAlphaBlendFactor = MTLBlendFactor.SourceAlpha;
        pipelineStateDescriptor.colorAttachments[0].destinationRGBBlendFactor = MTLBlendFactor.OneMinusSourceAlpha;
        pipelineStateDescriptor.colorAttachments[0].destinationAlphaBlendFactor = MTLBlendFactor.OneMinusSourceAlpha;
        pipelineStateDescriptor.depthAttachmentPixelFormat = .Depth32Float
        pipelineState = try! device.newRenderPipelineStateWithDescriptor(pipelineStateDescriptor)

        let depthStencilDescriptor = MTLDepthStencilDescriptor()
        depthStencilDescriptor.depthCompareFunction = .Less
        depthStencilDescriptor.depthWriteEnabled = true
        depthStencilState = device.newDepthStencilStateWithDescriptor(depthStencilDescriptor)



let renderPassDescriptor = MTLRenderPassDescriptor()
        renderPassDescriptor.colorAttachments[0].texture = drawable.texture
        renderPassDescriptor.colorAttachments[0].loadAction = .Clear
        renderPassDescriptor.colorAttachments[0].clearColor = MTLClearColor(red: 1.0, green: 1.0, blue: 1.0, alpha: 1.0)
        renderPassDescriptor.colorAttachments[0].storeAction = .Store
        renderPassDescriptor.depthAttachment.loadAction = .Clear
        renderPassDescriptor.depthAttachment.clearDepth = 1.0
        renderPassDescriptor.depthAttachment.storeAction = .MultisampleResolve
        let commandBuffer = commandQueue.commandBuffer()
        commandBuffer.addCompletedHandler { (commandBuffer) -> Void in
            dispatch_semaphore_signal(self.bufferProvider.avaliableResourcesSemaphore)
        }
        renderEncoder = commandBuffer.renderCommandEncoderWithDescriptor(renderPassDescriptor)
        //For now cull mode is used instead of depth buffer
        renderEncoder.setCullMode(MTLCullMode.Front)
        renderEncoder.setDepthClipMode(.Clip)
        renderEncoder.setRenderPipelineState(pipelineState)
        renderEncoder.setDepthStencilState(depthStencilState)

Answer 1

I have finally soved it by the following function:

class func defaultSampler(device: MTLDevice) -> MTLSamplerState
    {
        let pSamplerDescriptor:MTLSamplerDescriptor? = MTLSamplerDescriptor();

        if let sampler = pSamplerDescriptor
        {
            sampler.minFilter             = MTLSamplerMinMagFilter.Linear
            sampler.magFilter             = MTLSamplerMinMagFilter.Linear
            sampler.mipFilter             = MTLSamplerMipFilter.Linear
            sampler.maxAnisotropy         = 1
            sampler.sAddressMode          = MTLSamplerAddressMode.ClampToZero
            sampler.tAddressMode          = MTLSamplerAddressMode.ClampToZero
            sampler.rAddressMode          = MTLSamplerAddressMode.ClampToZero
            sampler.normalizedCoordinates = true
            sampler.lodMinClamp           = 0
            sampler.lodMaxClamp           = FLT_MAX
        }
        else
        {
            print(">> ERROR: Failed creating a sampler descriptor!")
        }
        return device.newSamplerStateWithDescriptor(pSamplerDescriptor!)
    }