[Bf-committers] New "merge cdlayers by name" feature can generate more than 8 allowed uvmaps or vcol layers

[Bastien Montagne]

When you merge two meshes with each 8 UVMaps which names are not 
matching, you get a mesh with 16 UVMaps (same goes for vcol layers).

This is not completely bad per se, as the 8 limitation is only at the 
shading (render) level. However, we should try to fix it - here are some 
solutions I can see:

1) Let code as it is currently, warning the user when too much layers 
get generated, and add tools to merge layers (in a same object).
2) Just drop the layers above limit number (easy to implement, but not 
user-friendly at all!).
3) Fallback to "non-matching-name" merging when we do not have enough 
room to create all needed layers (not really good solution either, imho, 
as it would give some rather unpredictable results on user POV).

So I would rather go for 1)… We would probably also need some API from 
customdata.c to easily check the max number of layer is respected, and 
optionally merge or drop the supernumerary ones.

Any feedback is welcomed here, as usual, especially if you have better 
ideas on how to handle this issue!

Best regards,
Bastien