Blending for the MTLPixelFormat.r8Unorm texture

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Created Jul ’20

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Is it possible to have correct blending with MTLPixelFormat.r8Unorm texture?

Here is what I use now but it works wrong:

Code Block 		private func createBrushDescriptor(library: MTLLibrary) -> MTLRenderPipelineDescriptor {
				let vertexDescriptor = MTLVertexDescriptor()
				vertexDescriptor.attributes[0].format = .float2
				vertexDescriptor.attributes[0].offset = 0
				vertexDescriptor.attributes[0].bufferIndex = 0
				vertexDescriptor.layouts[0].stride = 2 * MemoryLayout<simd_float1>.size
				vertexDescriptor.layouts[0].stepFunction = .perVertex
				vertexDescriptor.layouts[0].stepRate = 1
				
				let descriptor = MTLRenderPipelineDescriptor()
				descriptor.vertexFunction = library.makeFunction(name: "brush_vertex_function")
				descriptor.vertexDescriptor = vertexDescriptor
				descriptor.fragmentFunction = library.makeFunction(name: "brush_fragment_function")
				descriptor.colorAttachments[0].pixelFormat = .r8Unorm
				
				descriptor.colorAttachments[0].isBlendingEnabled = true
				descriptor.colorAttachments[0].rgbBlendOperation = .add
				descriptor.colorAttachments[0].sourceRGBBlendFactor = .one
				descriptor.colorAttachments[0].destinationRGBBlendFactor = .one
				
				descriptor.depthAttachmentPixelFormat = .invalid
				
				return descriptor
		}

But it works wrong.

Answered by Ivan85 in 623723022

In my case this configuration helped:

Code Block descriptor.colorAttachments[0].isBlendingEnabled = true
descriptor.colorAttachments[0].rgbBlendOperation = .max
descriptor.colorAttachments[0].sourceRGBBlendFactor = .one
descriptor.colorAttachments[0].destinationRGBBlendFactor = .one

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Answer 1

Ivan85 OP

Jul ’20

Accepted Answer

In my case this configuration helped:

Code Block descriptor.colorAttachments[0].isBlendingEnabled = true
descriptor.colorAttachments[0].rgbBlendOperation = .max
descriptor.colorAttachments[0].sourceRGBBlendFactor = .one
descriptor.colorAttachments[0].destinationRGBBlendFactor = .one

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