gl_clear
This variable will toggle the clearing of the screen between each frame. This can be helpful when specing a game and flying out of the map and during map development when the map maker must fly outside of the map to look has his map from the outside. Enabling this toggle will clear the areas which are not rendered outside of the map thus preventing the flickering effect when images repeat themselves over and over. However it causes problems when playing and going through the surfaces of a liquid (for example when diving into liquid), as you will see a red flash where the liquid texture would normally be repeated.
On.
Off.