Moiré error

In Doom versions before v1.4, the Moiré error is a bug that took effect when the player got close to a wall in a room with a ceiling 560 units or higher. The screen would flash in a pattern quasi-randomly, although it got worse the taller the room was.

It was fixed in version 1.4.

The Moire error in a custom WAD file. 2 sectors: Sector 0 is 96 units high with CEIL5_2, Sector 1 is 9992 units high with FLAT22.