I am facing this problem where the label for the pointplacemark using the NASA worldwind API is not hidden behind terrain. The symbol hides but the label doesn't. It uses javax.media.opengl.GL and TextRenderer. If anyone has any idea about this problem, please share your views and do let me know if you need any other input.
You can see the problem in a similar thread at: http://forum.worldwindcentral.com/showthread.php?42600-PointPlacemark-label-is-not-hidden-by-the-terrain