Posted by Evert B on Jun 27, 2010; 5:59pm
URL: https://forum.jogamp.org/Extracting-projected-coordinates-tp835912p926002.html

I'm not so sure if I understand your question.

If you want to get the 3D world coordinates of a 2D point on the screen: you can use GL selection API's as Demoscene Passivist pointed out or any one of many "picking ray" solutions.

If you want to get the 2D screen coordinates of a point in 3D world space (which is what I think you want): you should be able to just transform your point using the modelview and projection matrices - which you can extract from GL or build yourself - and then multiply with the dimensions of your screen. Ask if you need any more info.