I have the following problem: We are developing code using particle in cell algorithm and we'd like to use CAD models as an input. Thus we need to divide 3D model given in STL format(that is given by surfaces) to particles. At first calculation step it's ok to divide it to cuboid particles, that is represent all bodies in the model as constructed from cubes. May be it will be more clear if I formulate my question more strictly:

I have 3D model given by STL file ( suppose it has been exported from any CAD system) and uniform orthogonal grid. I need program or algorithm which can tell whether given grid cell contain part of body or not. It's desirable to calculate volume of body lying in any given cell and if there are parts from several bodies in this cell then appropriate volumes of each body. But single yes or no is also ok.

I'll be thankful for any help or hint where to find information on the question.

I think that CATIA5( a CAD/CAM package) will do what you have described. I'm not sure whether the earlier version will do it (CATIA4), which runs on UNIX will do it. -Go with the Flow; Edward