Stores the front clipping plane offset from the target plane for the current viewport, in drawing units.
The front clipping and front clip not at eye bitcodes in VIEWMODE are on. The FRONTZ value is the last front clipping plane value set current with the CAMERA, DVIEW, or 3DCLIP command. The distance of the front clipping plane from the camera point is found by subtracting FRONTZ from the camera-to-target distance.