PM record / pm multiplexor

[Heaven/TQA]

as there is a nice discussion going on in the retro gamer forum regarding what atari can do with its flexible hardware i post here my sprite multiplexor done 2003 and reworked 2005. some of you might remember.

 

the demo shifsts 16 8x8 1 colour PMs per VBL around (PAL) and moves them randomly (!) around. the flicker is happening when there are more than 4 player on 1 scanline and this seems not to be handled correctly at the moment. the additional sprites on such scanlines should be rejected and not displayed.

 

anyway... why i am posting that here? simply because atari build a nice hardware but the sprite engine is really a pain where other computers have a better hardware.

 

how is it done?

 

well... the idea is that there are situations where you can split across a screen the players around by DLIs. you can see the DLIs (white line) in such zones 4 virtual objects are mapped to the 4 hardware sprites and in the next zone same happens. so we do not care which hardware player is used for which virtual sprite.

 

the core engine is to SORT the virtual players by their y-position so you can easily draw them from top to bottom.

 

why did i wrote such a thing?

 

simply because i wanted to know how flexible such a system can be and how many CPU time is consumed by such a engine. as some people claim "yes. you can easily spread PMs across the screen by DLIs." which is true. but what they forget is that there is an aditional logic behind such a system needed:

 

1) sorting

2) building the DLI chain

3) moving the 16 virtual sprites

4) coping the PM data into the virtual slots.

5) copy the stuff on screen

 

what is still missing is a potential game logic moving such players in patterns etc or scrolling the screen or checking collisions. collissions all have to be done in software as you can not use hardware.

 

i hope you are not disppointed but esp. pm grafix for games you can not get for free. even you think of using them instead of soft sprites...

 

and if you think that this is kind of lame and could be done better... feel free to show me you multiplexor... inkl. music and doing more than 16 8x8 PMs. but do not "cheat" by precalculating the movement where you could avoid overlapping etc... free random movememnt please...

PLEX8.zip

Edited June 3, 2007 by Heaven/TQA

[Shawn Jefferson]

I remember you posting this before. Looks pretty good, but doesn't work in NTSC mode, I guess because of all the data moving you are doing in VBI ? For use in a game, you could probably get away with not completely random movement and the engine would be faster.