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I work in the game industry and often make shaders that rely on vertex color parameters for certain effects. This is often used to reduce shader complexity and material usage in order to improve performance. I normally paint the vertex color values in Blender, but there doesn't seem to be a way to paint the alpha component of the vertex color. Is there any way to set vertex color alpha?

Unrelated to the question, but it would also be awesome if there was a simple way to filter color channels in vertex paint mode like in Photoshop's channels box :)

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2 Answers 2

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An alpha channel exists for the Attribute node with support for vertex color since Blender v2.92 came out back on February 25, 2021 (see release notes).
But since v2.81 released on November 21, 2019 (see release notes, there is a dedicated Vertex Color node. You can use either of these nodes.

Vertex Color node (v2.81 and higher):

vertex color node

Attribute Node (v2.93 and higher):

Check that your Vertex Color Index name is correct. By default it is "Col".

In Vertex Paint Mode, to paint vertex color alpha data, use the Add Alpha or Erase Alpha blend modes in Brush Settings:

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  • $\begingroup$ Thanks for the additional details @L0Lock $\endgroup$
    – Mentalist
    Commented May 26, 2022 at 9:23
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There is no alpha component in vertex colors in Blender. The property is array with size 3, not 4.

You can have any amount of Vertex color layers though.

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  • $\begingroup$ The answer makes me a little bit sad, but thanks :( $\endgroup$
    – MrFlamey
    Commented Dec 9, 2015 at 14:28

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