I was wondering if / how this is possible in Blender.
Shaders in game engines like unity and unreal read texcoords (aka UVs) as Vector4 properties. Blender seems to deal with these mostly as Vector2.. however this can be quite useful. For example I have packed a different set of vertex normals into the UV2 texcoord using code in unity but that approach is quite cumbersome and not as flexible as doing it in blender when really working the model.
How can I put a Vector3 information into a uvmap / texcoord? (this would also allow multiple vertex color sets in an exported fbx). thanks for your answers.