In our new plug-in we use conduits to display simulation results using a

collection of dense surface meshes. We want users to be able to pick

points on the surface constrained to any of these meshes… like

GetPoint.Constrain() except with multiple meshes.

So I think we have to do the picking geometrically with mesh-line

intersections, except using `Geometry.Intersect.Intersection.MeshLine()`

will not register an

intersection if the user picks precisely on a vertex. One solution

seems to be to perform multiple mesh-line intersection tests in the

neighborhood around the pick point, then use the nearest vertex if it is

within some epsilon of the nearest identified intersection point.

Does anyone have any other ideas to allow users to select points

constrained to be on the surface of a set of meshes?