I’m not sure when this changed but i know it is different in 2.66 (i’ve been using it as a work around)
When you merge 2 or more objects in blender the old behaviour was to combine vertex colours and UV maps.
for example if you merged object ‘a’ and object ‘b’…
If object ‘a’ had a UV set called ‘UVMAPA’ and ‘b’ had ‘UVMAPB’
If ‘a’ as the active object the result would be an object ‘a’ with a UV map ‘UVMAPA’ that contained the unwrap from “UVMAPB”
now in 2.71 I get a new object with 2 UV maps ‘UVMAPA’ & ‘UVMAPB’… this may seem sensible but the ‘UVMAPA’ contains no unwrap information for the faces that were formally object ‘b’… which makes material setup more complicated because UV layers have to be set, where as if it was all in one I could just let it use the active UV layer.
It is the same for vertex colour data. vertexes not part of the original vertex colour layer are left white.
If both objects have a UV layer or vertex layer that are named the same they do get merged. But I have many meshes imported that have differently named uv layers so i have been loading them in 2.66> joining them> then copying back to 2.71
Anyone Know of a work around for this new behaviour? like a merge UV layer option or something.