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Shadow
Account closed
Registered: Apr 2002
Posts: 355 |
Is 120 the max number of full height sprites that can be displayed?
I've been on a nostalgia trip and checking out some demos from the real oldschool, record-breaking times. So I started thinking a bit about the world record for most sprites in a multiplexer. I started calculating, and got the following:
8 sprites can be displayed per 21 lines (since a sprite is 21 pixels high). Now you have 256 y-positions available to place sprites on. That should give us 96 or maybe 104 (I wasn't quite sure on this).
Since I saw demos with 112 and even 120 sprites (think it was in Ice Cream Castle/Crest), this couldn't be the limit.
Anyway, I started coding on a little test program and discovered that sprites placed on position $01 to $1e was displayed twice (both in the upper and lower border. I guess this is common knowledge, but I've been out of the loop for a while!)
Now, those $1e lines gives us the possibility to display two batches of 8 sprites that essentially gets doubled, thus we have 104+116 = 120 sprites as the absolute maximum.
Is this correct reasoning? Any oldtimer hardware specialits who can shed some light on this? |
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Shadow
Account closed
Registered: Apr 2002
Posts: 355 |
Umm.. that last calculation should read "104+16" ofcourse. |
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Steppe
Registered: Jan 2002
Posts: 1510 |
AFAIK the Crest demo uses a technique that reduces the height of a sprite to 17 pixels and thus achieves the higher amount of sprites. Not sure if it has to do with the doubling of sprites you described. |
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T.M.R
Account closed
Registered: Dec 2001
Posts: 749 |
Ice Cream Castle does 120 and as far as i know that's the upper limit without using something to shorten the sprites. Krestage does 144 with tricks to make the sprites 17 pixels high. |
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Shadow
Account closed
Registered: Apr 2002
Posts: 355 |
Alright, thanks for the info guys. Looks like I was on the right track with my calculations then. |
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Stryyker
Registered: Dec 2001
Posts: 468 |
If you're curious and want to try the sprite shrinking, it's anti sprite streteching which the VIC Article details (to the cycle). Just reverse the writes I think. |
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Ninja
Registered: Jan 2002
Posts: 411 |
stryyker: Not exactly. If the store instruction which sets the $D017-bits is exactly at a certain cycle, the sprite-data-pointer is messed up. Crossbow has made some effort to create a table, which shows how it gets confused (anyone verifyed this table?). It is included in the world-record-multiplexer in "Krestage 1" (press RUN/STOP). |
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Shadow
Account closed
Registered: Apr 2002
Posts: 355 |
Wow! Thanks for letting me know about "Krestage". There's a very good explanation on the whole sprite multiplexer issue, with 112/120 sprites etc.
Btw. I hadn't seen that demo before. What a brilliant piece of absolute hardcore coding! That text-mode, I was just blown away! I thought I had turned on my Amiga by mistake! :) I just don't understand how you can get that half-pixel X-interlace thing going. Crossbow is unbelivable!
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JCB
Account closed
Registered: Jun 2002
Posts: 241 |
Nice bit of code, but a multiplexer? I don't think it can be classed as one. Standard y movement doesn't need a multiplexer sort to decide which sprites are on which raster, just have a routine that draws 8 sprites at a time at various positions down the screen then move the appropriate x,y,colour and defininition list round in a cyclic buffer and its all done, no sorting needed, imho can't class it as a multiplexer without the sort :P |
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cadaver
Registered: Feb 2002
Posts: 1160 |
Ah, the gameprogrammer's perspective :)
But this would imply the boss enemy routines in Turrican or Armalyte aren't multiplexers either? (because they don't need to be sorted)
I'd guess the beauty in demo-multiplexers is especially the error-free display, in addition to large amount of sprites. This is something that game-multiplexers (general, sort-based approach) will always fail in, with sufficiently tight sprite formations
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Warbaby
Account closed
Registered: Mar 2002
Posts: 60 |
In my oppinion, there are two cathegories of multiplexers:
standard multiplexers
sorting multiplexers
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