Interactive video compositing
Interactive video compositing, or IVC, is an interactive media production technique that uses pre-rendered videos and images to create visual coherence, allowing interactive environments to be created without the heavy processing load incurred by real-time 3D graphics. The most popular examples of IVC are in video games using the technique prior to the propagation of real-time 3D graphics.
Source: Wikipedia — Interactive video compositing (CC BY-SA 4.0)