Havok (software)
From Halopedia, the Halo wiki
The HAVOK Physics is a physics engine developed by Irish company Havok and has been used by a large number of projects, both in the video game and movie industries, by using dynamic simulation to simulate physical interactions realistically, including such features as ragdoll physics or intelligence in massive falling objects. A glitch with the engine is visible when a player enters unprocessed areas, causing previous images to merge with current ones.