Many games used this technique for a scrolling star-field, but sometimes a more intricate or multi-directional effect is achieved, such as in the game Parallax by Sensible Software. This software effect gives the illusion of another (hardware) layer. Color cycling can be used to animate tiles quickly on the whole screen. Scrolling displays built up of individual tiles can be made to 'float' over a repeating background layer by animating the individual tiles' bitmaps in order to portray the parallax effect. For instance Star Force, an overhead-view vertically scrolling shooter for NES, used this for its starfield, and Final Fight for the SNES used this technique for the layer immediately in front of the main playfield. Programmers may also make pseudo-layers of sprites-individually controllable moving objects drawn by hardware on top of or behind the layers-if they are available on the display system. There are three main methods to simulate parallax scrolling in home computer or video game console systems that to not support multiple background layers. Many arcade system boards, especially from Sega, Capcom, and Irem, as well as Sega's Mega Drive and Saturn consoles, support the scrolling of individual rows and/or columns of a tilemap ( ref) ( ref) This allows the hardware to either produce parallax scrolling effects from a single tilemap, or add more layers of scrolling to increase the depth of parallax scrolling. Layers can be placed in front of the playfield-the layer containing the objects with which the player interacts-for various reasons such as to provide increased dimension, obscure some of the action of the game, or distract the player. Layers that move more quickly are perceived to be closer to the virtual camera. On such a display system, a game can produce parallax by simply changing each layer's position by a different amount in the same direction. Some display systems support multiple background layers that can be scrolled independently in horizontal and vertical directions and composited on one another, simulating a multiplane camera.
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