VISION

There are three primary types of "seeing" things. They are:

lightsight   Regular vision based on light, also called lightvision.
infravision  Vision based on sensing heat, also called heatvision.
deadeye      Vision based on sensing life, also called lifevision.
             This is how the undead see.

Most creatures see using lightsight with many races also getting the ability to use infravision. Undead, however, see using deadeye instead of lightvision.

Please read VISION-EXAMPLE for an example of how vision works.