Perception Ranges:2DA

From NWN2Wiki

Rich Taylor:

Primary Range is the Spot range (Visual range) Secondary Range is the Listen range (Hearing range)

If something is flaged as PercepRngDefault, instead of reading the values from the columns on that row, it looks up the creature's Appearance in Appearance.2da and uses the PERCEPTIONDIST column to find out what row creatures with that appearance are supposed to use. PERCEPTIONDIST in appearances.2da should reference back to a row in ranges.2da from which to read the values in from.

If all else fails, a creature will be assigned the values stored in the PercepRngMin row.