Rob having provided precisley what Nurbs are also gave you a valuble link to go check out- Rhino the mighty and powerful NURBS modeler. McNeel let's you download Rhino and try it for If I recall 20 times before it becomes unusable. I still have 2 turns left.(Try sweep 2 rails if you download it :) I'm saving those turns for very well planned out models. Hand drawn with all things worked out on paper first. Rhino's limitation is it's rendering isn't the best however it imports into RayDream and other 3d programs in a variety of 3d formats including COB for Truespace. Blues-