UV maps that are used for surface attachment must not have overlapping
uv islands, because then the same uv coordinate would correspond to
multiple surface positions.
Ref T99936.
Previously, curves sculpt tools only worked on original data. This was
very limiting, because one could effectively only sculpt the curves when
all procedural effects were turned off. This patch adds support for curves
sculpting while looking the result of procedural effects (like deformation
based on the surface mesh). This functionality is also known as "crazy space"
support in Blender.
For more details see D15407.
Differential Revision: https://developer.blender.org/D15407
This splits out the code that samples points on a surface and the
code that initializes new curves. This code will be reused by D15134.
Differential Revision: https://developer.blender.org/D15216
