First of all, you should open new topics for new questions, as one otherwise tends to derail old topics, which makes it hard to for others to follow things later. I forked your topic.
And I also do not quite understand what your question is. GetClosestMeshPrimitive returns you the primitive type via primInfo.
When you only want to get the closest point on a mesh, I would build a KD-Tree for its vertices. You then get the closest vertex and its index for your point p. Then you orthogonally project p onto the polygons attached to that vertex (via cinema:: Neighbor). Then you chose the closest point. We have this Python example for KDTree and I also used Neighbor there. Building a KD-tree or just brute forcing it depends a bit on how often you want to do it. For just a handful of points, brute forcing it is usually faster.
I am sure you can also do this with DistanceQueryInterface and the uvw coordinate returned in the PrimitiveInformation, but all that extra work where you have to deal with all the primitive types seems like more work than it is worth. And when you want to do this in a generator (by the looks of your screens), using a manual KDTree approach will make it easier to parallelize it effectively and make it go zoom zoom instead of computing all that extra data.
Cheers,
Ferdinand
