MathMod is a mathematical modeling software. It is a rewriting of K3DSurf by the same author.
New features and better materail supports are present in this new project.
For example, it can export to the OBJ file format.
The new Opensapce3D version can import OBJ file format. I didn't try it but you can try and tell us your feedback about this.
MathMod main site : http://sourceforge.net/projects/mathmod/
Download : http://sourceforge.net/projects/mathmod/files/