Extracting clipped geometry from the pipeline

I’m trying to use frustum clipping to alter a mesh, extracting the subset of the original mesh that falls within the view frustum. As such, I need to extract the vertex and polygon data from the pipeline after the clipping step, but before scan conversion. Is this even possible? All I need are the vertex and polygon lists, from which I can reconstruct the clipped model.

Advice is appreciated

• tetracanth

Not really possible with OpenGL alone.
This seems to be more suited to your task :
http://gts.sourceforge.net/gallery.html

hmm, GTS seems to be nice library for LOD generation.

You can use glRenderMode(GL_FEEDBACK) to get
vertices /polygons before clipping (but after vertex
programs) and clip it yourself.
Clipping is done by very simple equation and one compare.