Hi Chris,

> I thought OBJ had support for nurbs surfaces (or at
> least spline surfaces) but I have never come across any
> applications that write nurbs/spline surfaces to OBJ files.
>
> Do you have any idea why developers don't use this function?

It's basically a chicken & egg problem - most programs don't write NURBS data to OBJ files because there aren't many programs that read NURBS data from OBJ files. And most programs don't read NURBS data from OBJ files because there aren't many programs that write NURBS data to OBJ files.

Rhino does have an option to write a NURBS OBJ file, but as far as I can tell it is rarely used. I think PolyTrans is another application that can read NURBS OBJ.


A lot of programs that use OBJ format are polygon based programs that don't use any NURBS functions themselves, so that's another reason.


- Michael