Mesh stores its dvert in a specific pointer too, in addition of regular CD layer...
That whole vgroup handling is really breaking apart the 'universality' of CD system. :(
Also added some DAG and WM updates in operators...
Needed to replace weight transfer modifier in WeightPaint mode...
Note this is not exposed to users in UI, shall remain technical intern
parameter imho. Esp. since behavior when several sources is a bit 'random'
(merely uses each source in selection order...).
Also, this correct a bug, where 'lib' linked objects/meshes could not be used
as source...
Not much to add, modifier uses same code as operator basically, only key difference
is that modifier will never create data layers itself, you have to use dedicated operator
for that.
This add code needed to map a CD data layout from source mesh towards destination one,
and code needed to actually transfer data, using BKE's mesh remap generated data.
This allows to transfer most CD layers (vgroups, vcols, uvs...) as well as fake, boolean ones
(like smooth/sharp edges/faces, etc.). Some types are not yet transferable, mainly
shape keys, this is known TODO.
Data transfer can also use some advanced mixing in some cases (mostly, vgroups and vcols).
Notes:
* New transfer operators transfer data from active object towards selected ones.
* Modifier will be committed separately.
* Old weight transfer code (for vgroups) is kept for now, mostly because it is the only
usable one in weightpaint mode (it transfers from selected object to active one,
this is not sensible in Object mode, but needed in WeightPaint one). This will be addressed soon.
Again, heavily reviewed and enhanced by Campbell, thanks!
