The clip command controls clipping planes. Up to four planes can be active:
Each plane can be activated or turned off individually; specifying an offset activates a plane if it was not already active. Offsets are in physical distance units (generally Å), with positive values increasing away from the viewer for the near/far planes. The offsets are relative to the position reference point, if given. Otherwise, offsets are relative to the current positions of the planes, or (if a plane is newly activated) the center of the bounding box of displayed models. The position of a plane is forgotten when it is turned off.
The position refpoint can be given as:
The axis option sets front/back plane orientation, where the normal (the axis perpendicular to the plane) can be given as:
The coordinateSystem for interpreting position and axis coordinates can be specified by reference model number. Otherwise, the screen coordinate system (X horizontal, Y vertical, Z in/out of screen) will be used. The default initial orientation of front/back planes is normal to the screen Z-axis or line of sight.