Posted by Demoscene Passivist on Jan 09, 2011; 12:46am
URL: https://forum.jogamp.org/Selection-rectangle-over-complex-scene-tp2218866p2219312.html

As Wade already suggested making a snapshot by copying the current framebuffer is one way to go, but on hardware that supports "Frame Buffer Objects" (wich nearly all GPUs still alive should)  u should definitly render ur scene to texture directly. Its much faster.

Ur scene would then be only composed of the FBO billboard + the overlay billboard rendered on top of that with additive blending mode or alpha channel blending. U could then independently update ur scene or the overlay.