Webster's defines a gnomon as ``an object that by its position... serves as an indicator.'' In 3D PyGist, the gnomon is a small diagram of the coordinate axes that appears in the lower left corner of a 3D plot, if this capability has been turned on.
gnomon ( [onoff] [, chr = <labels>] ) set_default_gnomon ( [onoff])
set_default_gnomon allows the user to specify what the default
gnomon is to be when the default idler is called (see the discussion in ``The variable _draw3 and the
idler'' on page ![[*]](crossref.png)
, and ``The Default Idler'' on page .)
The gnomon shows the x, y, and z axis directions in the object coordinate system. The directions are labeled. The labels default to X, Y, and Z, but may be specified to be something else by using the keyword chr. <labels> must be a Python list consisting of three character strings. The gnomon is always infinitely far behind the object (away from the camera).
There is a mirror-through-the-screen-plane ambiguity in the display which is resolved in two ways: (1) the (x, y, z) coordinate system is right-handed, and (2) If the tip of an axis projects into the screen, its label is drawn in opposite polarity to the other text in the screen.