The walkmesh of an area covers the surface of the area, indicating where a character can actually walk. Obstacles—such as trees, buildings, rocks, and placeables—create "holes" in this walkmesh where characters cannot travel. Static placeables create holes in this walkmesh when the area is being loaded (i.e. only needs to be done once per area load), whereas non-static placeables dynamically affect the walkmesh every time a character comes close enough to see them (i.e. done fairly often in case the obstacles disappear).