Geo Nodes Vertex Colours don't export with FBX

Hi all!
I’m working on a geometry nodes landscape generator that uses Vertex Colours to blend textures in the shader. It works great until I export the mesh as an FBX or even just apply the GeoNodes modifier in Blender. After I Export/Apply the Vertex Colours they are just white as if they hadn’t been set by the GeoNodes at all.

I’m setting the Vertex Colours with the Capture Attribute node, I’d like to use this more but I’m not sure how to make the Vertex Colour Data actually export with the mesh.

I’d appreciate any advice on getting this to work, or even just confirmation if this technique is a dead end.

Does this work?:

  1. Create a color attribute on the mesh data that matches the name of the attribute you wish to store it to.
  2. Use the same name in the modifier panel to store the attribute.
  3. Apply the geometry nodes modifier to the mesh (after duplication if necessary).
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I’ve tried that with a blender 3.3 build that is a mount old :

I create an attribute called Color, and in the GN tree I override it, once I apply the modifier the new color is set to the ‘Color’ attribute.

If I create the attribute right in the node tree (without creating it beforehand) , then once the modifier is applied that attribute is added in the Attribute panel.

Sounds like it’s working quite well this way, I didn’t test the method you mentioned but that could work too !

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@sozap nailed the attributes, following your steps gets the colors into the mesh, then I followed up with info from these bug reports to go from Blender to FBX:
https://developer.blender.org/T72983
https://developer.blender.org/T98721

Here are the steps that ended up working, seems like FBX and Color Attributes (Vertex Colors were replaced by attributes) don’t play very well, but it does work.

The important part is to store the colors as Byte Color in the Face Corners. Anything else won’t encode in the FBX (as documented in the above links).

The bottom is generated Vertex Colours from Geo Nodes, the top is after the nodes are applied with some manual Vertex Colour painting.

And here they are in unity as an FBX, works like a charm! The bottom is generated, and the top is applied Geo Nodes with the hand painting.

Thanks for helping me out! I really appreciate it.

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