Foxes are crafty, and Skyrim's foxes are apparently doubly so. For years, players believed the helpful lil' critters were leading them to treasure in an act of kindness or perhaps some secret ritual pact between the Dragonborn and the innocent creatures of the wild.
It turns out the treasure-savvy foxes were a happy coincidence born out of Skyrim's complex AI control systems.
Skyrim senior designer Joel Burgess told the story on Twitter following Nathan Purkeypile's origin story about the famous opening cart scene and its bee troubles.
The Mystery of Skyrim's Treasure-Hunting Foxes Is Solved
Burgess explained that Skyrim uses several layers of navmesh to dictate where AI-controlled NPCs and animals can go. That system has a further set of layers that guides the NPC's actions.
"In most situations, you're seeing AI decide what do to (run at player, hide in cover, etc), use navmesh to make a path, and navigate along that path," Burgess said. "Foxes are no different. But their AI is very simplified: they basically can *only* run away. If you spook a fox, it flees."
High Process pathfinding kicks in for NPCs close to you, especially in combat, and helps them find lines of sight to make important actions, such as harming you fatally. Densely populated areas have thicker navmesh layers.
Low-range processing is less intensive, Burgess said, and is designed to run without refreshing for several minutes at a time, making it perfect for open areas.
In between is Medium Process, though Burgess and other programmers didn't know another designer had created it at the time. Foxes and their need to flee from you use this process. When they're running away, they're trying to get 100 triangles away from you.
"You know where it's easy to find 100 triangles?" Burgess said. "The camps/ruins/etc that we littered the world with, and filled with treasure to reward your exploration."
"So foxes aren't leading you to treasure - but the way they behave is leading them to areas that tend to HAVE treasure, because POIs w/loot have other attributes (lots of small navmesh triangles) that the foxes ARE pursuing."
Foxy mystery solved.