Horizontal blanking interval refers to a part of the process of displaying images on a computer monitor or television screen via raster scanning.
[citation needed] Some graphics systems can count horizontal blanks and change how the display is generated during this blank time in the signal; this is called a raster effect, of which an example is raster bars.
In video games, the horizontal blanking interval was used to create some notable effects.
Some methods of parallax scrolling use a raster effect to simulate depth in consoles that do not natively support multiple background layers or do not support enough background layers to achieve the desired effect.
One example of this is in the game Castlevania: Rondo of Blood, which was written for the PC Engine CD-ROM which does not support multiple background layers.