Why to write a program of this type, if already exist Geomview, and MathGL3d, for example?

Well, geomview is an excellent program that already has several years of development. In spite of it, it is not exactly what i wanted. In the first place, geomview uses Motif. Luckily lesstif exists, that at least allows to compile it.

In fact, my original plan was to port it to gtk. I was reviewing the code a couple of hours, and I realized that the program was of a greater complexity than I had in mind. What I wanted was a simple and efficient program, and easy to maintain. So I decided to begin from zero.

MathGL3d also seems a nice program, but it's too tied with mathematica (i think), is written with glut and last time i checked, it does not allowed arbitrary rotations. mhhh...

And of course the main motivation is to learn, and to do something useful.