During hair grooming in curves sculpt mode, it is very useful when hair strands
are prevented from intersecting with the surface mesh. Unfortunately, it also
decreases performance significantly so we don't want it to be turned on all the time.
The surface collision is used by the Comb, Pinch and Puff brushes currently.
It can be turned on or off on a per-geometry basis.
The intersection prevention quality of this patch is not perfect yet. This can
be improved over time using a better solver. Overall, perfect collision detection
at the cost of bad performance is not necessary for interactive sculpting,
because the user can fix small mistakes very quickly. Nevertheless, the quality
can probably still be improved significantly without too big slow-downs depending
on the use case. This can be done separately from this patch.
Pull Request #104469
