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I suspect, but can't prove, that the answer is "No", as materials are meant to be portable. However, I don't see why we couldn't implement something that would at least look up the vertex group name to be sure and return a default value otherwise.

I'm working on some very visceral-looking alien architecture, and I assumed that I could use a vertex group (and its associated weight painting) as the factor input to a mix shader. However, when I go browsing through Input nodes for my material, even though I could swear this was in there at some point, I'm coming up with nothing.

I may end up doing something complicated involving a custom property and a sequence of drivers here, if I can't find it. Seems overkill for a material, but thems might be the breaks.

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  • $\begingroup$ Try an attribute input and set it to the vertex group name. It’s a long shot, but it works in geometry nodes. $\endgroup$ – TheLabCat May 31 at 3:13
  • $\begingroup$ It didn't work, but thank you, it was a great idea. I feel like it might still work if I could remember the path to the uv nodes. @ZargulTheWizard Do you think this might be a decent development suggestion or personal implementation? I mean we have vertex colors accessible (which is what I'll be doing next). $\endgroup$ – Michael Macha May 31 at 3:41
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Since Geometry Nodes, certainly in 2.93, you can reference any GeoNodes attribute in the 'Attribute' input to a shader tree. Strangely, I don't think you can get at a vertex-group directly (yet).

You can do it by transferring the weights to an attribute created in the GeoNode tree. (e.g.) Attribute Fill your chosen name with 0, and Attribute Math add the vertex-weights from the group to that name.

Pre GeoNodes, there's @Nathan's Wonderful Workaround :)

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  • $\begingroup$ Personally, I wish vertex-weights were a little more smoothly integrated into all other branches of the application, as they were in XSI. $\endgroup$ – Robin Betts May 31 at 8:48
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    $\begingroup$ That hack is genius. Here I was about to say that this was useful information but I'm looking at material nodes; then I notice this. Honestly I've done everything I need to do in a cleaner manner with texture painting; but thank you for this. $\endgroup$ – Michael Macha May 31 at 13:14
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So, after some digging, I've determined that the answer is effectively "no", most likely for the reasons above; but it's also redundant. You can easily simply UV-unwrap, and then texture paint any number of textures to carry your data in an R, G, B, or A channel; then reference the channel in the material. Or, given that your mesh is fine enough and you won't mind the interpolation, you can just paint vertex colors and reference the channels of those—which you can also have several of if you need them.

This in mind, weight painting has come to feel almost like a redundancy at this point, which gives me both questions about the future, and actually great ideas for it.

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