Difference between revisions of "Sprites Multiplexing"

Revision as of 21:51, 15 December 2009

Sprites Multiplexing is a technic often used on other machines with Hardware Sprite Capability.

It was often used on the C64.

On the Amstrad Plus range, it couldn't be used as well. But some possibilities exist.

It allows to "Multiplex" the same Sprite at different rasters lines.

Limitations of Sprites Multiplexing on Amstrad Plus

The technic impose some limitations due to the somewhat unachieved design of the Amstrad Plus and the complex specificity of the ASIC :

• The same Sprite is simply copied/duplicated as it is.
• No multiplexed sprites can be at the same Line.

Multiplexing on the PLUS is much more difficult than on the C64. The reason is that the location for the graphics are fixed on the PLUS. e.g. Sprite 0 always looks at &4000 in the ASIC sprite RAM. This can't be changed.

On the PLUS however you can freely change the X,Y position so it is possible to perform some multiplexing of the sprites.

Another way to multiplex sprites is to use screen rupture, because the sprite X,Y coordinate is based on the CRTC's Raster and Line Counter.

Possible uses

This can then be used for games like Shoot'emups... as the sprites don't always need to be well animated (just moved) and as enemies waves are often pre-determined (R-Type is the typical exemple).

So it fit well for Vertical Waves of enemies.

Also for vertical or even diagonal special effects.

Exemples of Sprites Multiplexing on an Amstrad Plus

This Technic wasn't really exploited on the amstrad Plus, mainly because the Amstrad Plus wasn't really exploited.

• Black Sabbath (first harware sprites multiplexing demo as claimed by its author) by BDC-Iron
• Delirium Tremens preview by BDC-Iron
• Maybe the Synergy demo.
• Probably It was so nice before the crash of the mir station

Video

• Sprite Multiplexing on C64 : http://www.youtube.com/watch?v=oyf2W239eRY
• Synergy Demo on Amstrad Plus : http://www.youtube.com/watch?v=YGH5JIPWQ2I

Other Sources and links

• Amstrad CPC plus sprite format
• Programming:CPC Plus Hardware Sprites

• Sprite Multiplexing Article at a C64wiki
• Sprite Multiplexing project on Nintendo DS