"Eavesdrop" on vertex shader output

Hello GLers,

I suppose my previous post about Transform Feedback was too biased towards a possible solution, so I try to restate my problem:

What is the easiest way to get read-only access to the vertex shader output. I want to do something like “Image Recognition” without having to deal with images In fact, I am only interested in the visible lines of a scene after they are projected to the viewport.

Regards and thanks,
Michael

Couple choices. Transform feedback as you say. Or a more expensive render-to-vertex-array (same thing, works on older hardware). OR, you could just do the matrix math on the CPU. Depends on your CPU, CPU, system, and GPU load which’d be faster. Just a question of perf.