Implicit to NURBS conversion

by Wu Jianbang for BRL-CAD

At present, BRL-CAD has implemented lots of geometric primitives in an implicit form, but when it comes to interactive shaded displays and conversion to other formats, the disadvantages of implicit primitives come out. So we need a conversion to NURBS bundary representations. Lots of primitives have already been implemented as NURBS, but some are not robust and some still need to be improved. Besides, some are still missing. This summer, if I'm accepted, I'm going to accomplish the goal of converting all (if needed) implicit primitives to NURBS, including fixing the bugs and correcting the errors existing now, and adding new conversions that have not been implemented yet. Finally, I'd like to build a converter that can walk a CSG tree and convert the implicit primitives in the tree altogether to their NURBS form. The original implementation in BRL-CAD is a good starting point, and I will take the current routines of BRL-CAD.