When there are 2+ consecutive deform modifiers, the second modifier was getting incorrect normals, this only showed up for the displace modifier since its the only deform modifier that uses vertex normals.
It would have been easy to fix this by always calculating normals on deform modifiers, but slow.
To fix this I added a function to check if a deform modifier needs normals, so the normal calculation function only runs if there are 2 modifiers in a row and the second uses normals.
* Problem was that the modifier directly accessed ob->derivedFinal, but that wasn't being built if the object was on a different layer. Changed to mesh_get_derived_final.
Notes:
* I fixed this for array and boolean, reported in the bug; there might be other places affected by this mistake. It's an easy fix if so.
* The datamask being passed in isn't especially correct. Possibly we should be accessing the datamask being used to build the array modifier DerivedMesh? Anyway, at least this will get the mesh to show up in the viewport.
patch by Ben Batt (artificer)
Updated patch for 6 or so modifiers added since the patch was written.
- tested with CMake and SCons
- fixed one error were flags were being added to the fluids type.
- remove BKE_simple_deform.h, simple_deform.c, move functions into MOD_simpledeform.c since there were problems with circular deps.
- moved some fluid and boolean functions used by modifiers too.
