Mode 7
The term Mode7 originated on the SNES video game console, on which it describes a graphics mode that allows a background layer to be rotated and scaled. By modifying the scaling and positioning of the layer on a scanline-by-scanline basis a simple perspective effect can be applied, transforming the layer into a 3D horizontal texture-mapped plane. Mode7-style rendering is generally used on systems with strong 2D capabilities but no dedicated 3D support. Classic Mode7 games include the SNES titles F-Zero and Super Mario Kart, both of which later revisited the effect in their Game Boy Advance incarnations. The SNES console has eight modes (numbered from 0 to 7) for displaying background layers, the last one having an actual perspective effect for a single layer at the cost of all others. The Game Boy Advance version only has scaling and rotation, on two layers, on modes 2 and 3. Combined with HBlank effects (changing the scaling/rotation values on each scanline), a very convincing "Mode7" effect can be achieved. On the SNES, a variation of Mode7 allows pixels of the background layer to be in front of sprites. Examples are Contra 3 (stage 2) and Tiny Toon Adventures (intro screen). Many PC games, most notably Wacky Wheels, have a Mode7 effect made by a completely software-based method. Mode 7 is also the name of the Teletext-compatible video mode available on the BBC Micro, noted for its colorful, blocky pseudo-graphics instantly recognisable by a generation of British school-children due to its use in many educational software programs in the 1980s.
|
