Well, basically I'm working on something that rotates 27 cubes around the screen. When I right click the mouse rotation is haulted and the player can click to place a marker on the cube. The problem is that I have no earthly idea how to translate the 3D Float points to something I can compare the X and Y with... any ideas?
You can either use picking, or gluProject/gluUnProject. That's as much as I know, unfortunately! I need to do the same kind of thing and haven't been able to get it working!
Here's a simple demo that does screen/world translations:
http://potatoland.com/code/gl/lwjgl_demoScene.zip
In GLApp_DemoScene.java, the functions mouseMove() and mouseDown() translate screen coords to world.
I wrap the gluUnproject calls in a base class function called getWorldCoordsAtScreen(), which may be helpful or annoying depending on how you like to code ;-)