If you disable depth testing (glDisable(GL_DEPTH_TEST)), any new line will be drawn over the old ones. That however disables the z-test, so also object that you would like not to see might be drawn then.
Yeah, DFrey, you’re always falling in my back with your idiotic answers. Geez. Well, just cleaned my room (or how’d you say?). Gives a great flair and feeling. You should clean your room as well! Well, I’m a bit unclean in the other time…