I've just upgraded to Quantal Quetzal on my home computer and discovered that the program K3dSurf has been removed from the repositories. (Presumably since it doesn't seem to be in active development and still depends on qt3 libraries.) Does anyone know of a similar program (user-friendly and versatile) for drawing 3D surfaces? This has been a mission-critical program for me when teaching multivariable calculus, so I won't be able to upgrade at work unless I can find a replacement. (Yes, I could install directly from the program's website, but dealing with obsolete libraries sounds like a giant headache.)