I have a very expensive scanner that scans gemstones and creates STL files. Problem is it creates an open mesh, I want it closed. The mesh has like a 90000 faces, so its hard to find out where it is exactly open. When I try to meshbooleandifference to use the scan as intended, there are all kinds of boolean issues due to the number of mesh. Reduce mesh only works down to a certain amount. Same if I use TONURBS. It becomes an open polysurface. There are so many poly surfaces and I cannot loft or cap it. Is there a way to like sub D a shell around this object ?
I know its hard to picture what I am talking about. is there a way to post the STL here so someone could help me out?
No (well, not really). If surfaces are not joining, the edges are out of tolerance. It is possible to use JoinEdge between two out of tolerance edge pairs to force the edges together to join. However, this does not change the underlying surface and its original edges and just results in a false sense of security. If you export these to some other program, they will come apart again. Even internally in Rhino some operations may fail with out of tolerance edges.
If you are working in NURBS geometry, you need to make sure that you create your objects to be joined within tolerance of each other. Otherwise, it’s a recipe for disaster.