43 lines
2.0 KiB
Markdown
43 lines
2.0 KiB
Markdown
---
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title: "Attachment Info"
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date: 2021-01-28T12:55:51-08:00
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weight: 0
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---
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GraphicsPipelineAttachmentInfo tells the graphics pipeline what kinds of render passes will be used with the pipeline. These are *compatible* render passes. It also describes how the pipeline should blend colors. Blending does not affect compatibility, but the other properties do.
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This structure is composed of a set of ColorAttachmentDescriptions, and an optional depth/stencil format.
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Each ColorAttachmentDescription is composed of a texture format, a multisample count, and a ColorAttachmentBlendState.
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Our color attachment always has color information stored in it - the blend state tells the renderer how to combine new pixel values with the original values to produce a new color.
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`BlendEnable` is a bool. If we turn off blending entirely, the new pixel color will just overwrite any existing values. Simple!
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`ColorWriteMask` tells the renderer which color channels it is allowed to write to.
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Next we have `AlphaBlendOp` and `ColorBlendOp`, which are `BlendOp` values, and the rest of the fields are `BlendFactor` values. Rather than spend a bunch of time explaining the nuances of various blend modes, I will simply link you to a [very thorough explanation of graphics blending](https://learnopengl.com/Advanced-OpenGL/Blending).
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Here is an example blend mode, which does something we call "additive blending". This kind of blending is very useful for lighting and particle effects.
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```cs
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var myColorTargetBlendState = new ColorTargetBlendState
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{
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BlendEnable = true,
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ColorWriteMask = ColorComponentFlags.RGBA,
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AlphaBlendOp = BlendOp.Add,
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ColorBlendOp = BlendOp.Add,
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SourceColorBlendFactor = BlendFactor.SourceAlpha,
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SourceAlphaBlendFactor = BlendFactor.SourceAlpha,
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DestinationColorBlendFactor = BlendFactor.One,
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DestinationAlphaBlendFactor = BlendFactor.One
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};
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var myColorAttachmentDescription = new ColorAttachmentDescriptions
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{
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Format = TextureFormat.R8G8B8A8,
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SampleCount = SampleCount.One,
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BlendState = myColorTargetBlendState,
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};
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```
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