I am trying to compute the center of gravity and mass moments of Pro/E solid models I have imported as STL's.  Once in Mathematica, the models are polygons that define the surfaces of the objects.  Does anyone have suggestions on how I can get Mathematica to treat these as boundaries that define a solid Region so I can numerically perform the integration?  I've done such integrals before, but I had mathematical expressions for the surfaces; now I only have data to define the surfaces.

I realize I could do this in Pro/E, but I am not myself a user of Pro/E, just a consumer.  Besides, eventually I want to calculations within SystemModeler based on data extracted from the solid models.

Thank you for the help,
Daniel