Generating triangulated mesh to complete a 3D object (in code or modelling software)

Here's the problem at a glance: http://i55.tinypic.com/2uy6nah.jpg

I have 3D models of teeth in STL format (simple binary/ASCII format storing triangulated mesh as a collection of facet vertices and normals).

Some of the models only have the top surface and no bottom (left figure). However, to be used as intended, they need to be transformed into a solid object (right figure).

It doesn't matter what shape the bottom part will be or how much height it will add to the object.

The STL files are currently processed by a C#/.NET program.

1. It would be great if I could generate that bottom mesh on the fly in software
2. Otherwise, it could be done manually in some 3D modelling software (preferably free or inexpensi开发者_开发技巧ve)

Looking forward to suggestions for both alternatives. Algorithms and/or links to relevant tutorials are always welcome..

I would argue that the normals are redundant. All you need are verticies and the connectivity for each triangle.

When I was doing finite element analysis for a living there were quadtree for 2D and octree for 3D automatic meshing algorithms. I think you want something like this:

http://www.ctcms.nist.gov/~langer/oof2man/Section-Tasks-FEMesh.html

I'm not sure how much of this is available for free.

If you're intending to do stress analysis on your tooth model you might consider boundary element methods. Unlike finite elements or finite differences, they don't need an interior mesh for linear problems.