In computer graphics, the hall of mirrors (HOM) effect is an effect in which a computer program attempts to draw an image of what is technically "nothing," and as a result of which, repeats whatever image is near to the null item, causing a shimmer or an endless repetition of an image, similar to the appearance of two mirrors reflecting each other, hence the name.
The concept of the hall of mirrors was popularized by the computer game Doom, where individuals have the capacity to create their own maps for play in the game. Some of these maps were not correctly set up with all proper binary reference points. In some cases, spaces in the map were not marked as being part of the map space, and were thus "void" or "null" areas. As these areas were visible from the player's perspective, these void spaces would create "holes" where the map was not correctly marked. These holes caused a "shimmer" effect and would repeat or "mirror" whatever else appeared on the screen at the time.