Parallax scrolling: Difference between revisions

Revision as of 08:04, 24 July 2005

Revision as of 01:38, 18 August 2005

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Some platforms ([[Super Nintendo Entertainment System|Super NES]], [[Sega Genesis]], [[Game Boy Advance]], [[Game Boy]]) provide a [[horizontal blank interrupt]] for automatically setting the registers independently of the rest of the program; others, such as the NES, require the use of cycle-timed code, which is specially written to take exactly as long to execute as the video chip takes to draw one scanline. Many NES games such as the classic ''[[Super Mario Bros.]]'' use this technique to draw their status bars, and ''[[Teenage Mutant Ninja Turtles II: The Arcade Game]]'' and ''[[Vice: Project Doom]]'' for NES use it to scroll background layers at different rates.

More advanced raster techniques can produce interesting effects. A system can achieve breathtaking depth of field if layers with rasters are combined; ''[[Sonic the Hedgehog 2 (Megadrive)|Sonic the Hedgehog 2]]'', ''[[ActRaiser]]'', and ''[[Street Fighter II]]'' used this effect well. If each scanline has it'sits own layer, the ''[[Pole Position]]'' effect is produced, which creates a pseudo-3D road (or in the case of ''[[NBA Jam]]'', a pseudo-3D ball court) on a 2D system.

If the display system supports rotation and scaling in addition to scrolling, an effect popularly known as [[Mode 7]], changing the rotation and scaling factors can draw a projection of a plane (''[[F-Zero]]'', ''[[Super Mario Kart]]'') or can warp the playfield to create an extra challenge factor (''[[Tetanus On Drugs]]'').