Amapi also had the ability to convert an SDS to a smooth Nurbs, BUT it could only handle about 100 polygons before crashing, and they were static objects. Not dynamic like a tspline. I've converted up to 80,000 faces in TSplines. So I think Amapi was doing some hacky reiterative patch solution and was not very efficient... But if you need a cheap converter for low-poly models only, you might still find it useful. But Amapi is pretty much deadware now...

jonah