This is mandatory for incoming custom normal imports from io scripts, because
often geometry here is corrupted, so we need to call mesh.validate() to clean it up.
Issue is, we cannot set custom normals before geometry is clean, so we need to store
temporary plain loop normals in a CD_NORMAL layer, validate, and then set custom normals.
So we need a way to prevent 'temp' lnors to be freed by validate.
Another Evil Typo (r) one, you could add much more than the 8 allowed VCol layers!
Note: added some (warning-only) checks in mesh validate functions, but we still have a big issue with new cdlayer merge function, which could generate more than 8 layers of UVs or VCol... Don't know yet how to handle this situation. :(
In fact, the issue was that names of mloopuv/mtespoly layers could very easily get out of sync (a simple rename was enough), while most tools (such as the UVProject modifier) expect matching layers to have the same name!
Now matching names are check on load, and renaming of a layer through RNA is guaranted to be synchronized with its counterparts.
Thanks to Brecht & Campbell for reviews.
old issue, the formulas here were never quite right, should all work ok now
with byte and float images.
Some differences:
* Colors with zero alpha from the background will never have an influence, so
you don't get alpha fringes when painting over such areas. This does give
hard edges when looking at the RGB channels alone, but there's no way to
avoid that and fringes at the same time, same behavior as other painting apps.
* Add/Subtract/Multiply/Lighten/Darken now leave the alpha channel unchanged
and work only the RGB channels, again same behavior as many other apps.
* Erase/Add alpha now compensates for premultiplied float images to keep the
straight RGB colors the same.
Next: fix projection painting.
Added back face validation to BKE_mesh_validate_arrays.
This is needed because some addons (like OBJ importer) are reading
tessfaces and then converting them to ngons and validation of tessfaces
is needed before such a conversion.
Validation of faces would happen only if there's no polys in mesh.
Everything seems to work well (many tests making random changes over various meshes went good), but the code is a bit complex and hard to follow, due to the various possibilities of invalid poly/loop combinations… Code also makes more operations than previous tri/quad faces version (hence is a bit slower), but I don’t think we can do otherwise, it’s just the price for bmesh flexibility. ;)
Note: added the py script I used to make the tests, under source/tests/...
