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To do: clarify: PAS is a kind of bounding-box for Player or NPC AI sound detection. It is measured as the set visleafs which are audible from the visleaf occupied by the Sensing NPC or Player. Similar to PVS, A PAS-test is only the first filter that a sound must pass in order to be audible to the NPC. (note: PAS is referred to in BSP compile log). See Talk:NPC_Sensing