Hi, I''m studing the diferent sorts of curved surfaces arround, because I would like to use them in several areas. Up to now, what I learned is that there is a big mess on the different names of the surfaces and its actual math formula... I haven''t found any good document that tells the difference between Bezier, Nurbs, Metanurbs, Splines, BSplines, and some other exotic agorythms (it seems that Pixar has a surface type on exclusive) I also learned that most surfaces are based on cubic or quadratic bezier surfaces, mostly on quadratic surfaces where there are 4 vertices and 12 control points arranged in this way: A 1 2 B 3 4 5 6 7 8 9 10 C 11 12 D where A-B-C-D are vertices and 1 to 12 are control points. My big question is: many commercial 3D editors that support curved surfaces seem to be able to edit ONLY the control points on the edges of the surface (control points 1,2,3,7,6,10,11,12) but there is no trace on how the control points at the center of the surface (4,5,8,9) are computed.... this leads me to think that the central points of the surface are generated on the fly based on the vertices and edge control points... my big question is HOW? Pd. one of the things I want to do is to be able to edit curved surfaces and export them to povRay, that requires all control points to be there. Any other info like links to documents on curved surfaces and how are they handled by commercial 3d editors will be appreciated.