We are developing some stress and strain analysis software at university. Now it's time to move from rectangles and boxes and spheres to some real models. But I still have little idea where to start.

In our software we are going to build mesh and then make calculations, but how do I import solid bodies from CAD/CAE software?

1) How CAD/CAE models are organised? How solid bodies are represented? What are the possibilities of DWG, DXF, IGES, STEP formats? There is e.g. a complete DXF reference, but it's too difficult for me to understand without knowing basic concepts.

2) Are there C++ libraries to import solid bodies from CAD/CAE file formats? Won't it be too difficult to build a complete model to be able to import comprehensive file?