recovering opengl's nurbs' mesh

Hi, I want to use the OpenGL nurbs’ mesh (resulting from renderization process) for my own purposes, such as creating objects like ‘node’, ‘edge’ and ‘element’. This will allow me to represent the mesh itself instead of the renderization of the nurbs.

The problem is: how can I recover the list of triangles that define the mesh?

thanks in advance!

GL_FEEDBACK.