Sprite split

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Par wimpie3

Champion (367)

Portrait de wimpie3

01-02-2021, 12:42

When my info is correct, Space Manbow uses a "sprite split" technique. Can anyone explain how this works? How many extra sprites can be shown on the screen? Was Space Manbow the only software to use this technique?

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Par lintweaker

Champion (411)

Portrait de lintweaker

01-02-2021, 12:59

Many games and demos use it. It can also be called 'line interrupt'.

http://map.grauw.nl/articles/split_guide.php

Par Sandy Brand

Master (235)

Portrait de Sandy Brand

01-02-2021, 13:01

I would like to know if this is actually true?

Whenever I look at replays it seems they use roughly 8 sprites for the player and its weapons, and 24 for enemies + bullets + explosions. But nothing more.

Most likely they alternate sprite priorities to counter flickering like many other games do, but I don't think there is actual sprite multiplexing going on there?

Par NYYRIKKI

Enlighted (5837)

Portrait de NYYRIKKI

01-02-2021, 13:16

MSX can show 8-sprites on a line, but other that that there are no hard limitations... In theory you can have own sprite set for each line on screen if 1-line sprite height is ok for you. Managing large amount of sprites on game like environment becomes anyway pretty CPU centered as you need to manually keep track what sprite sets your sprite needs to belong to. This makes sprite split techniques relatively difficult to use in games, but Space Manbow is a good example that it can be done.

Par Sandy Brand

Master (235)

Portrait de Sandy Brand

01-02-2021, 13:17

Hmm okay maybe I am wrong. For the player I can count:
fighter = 2
max 3 fighter bullets = 3
2 options = 2
max 2 bullets per option = 2 * 2 = 4
missile = 1
So this would be 12 in total for the player.

Which leaves roughly 20 sprites for the rest.

However, I can see the Lobster boss shoot 12 blue projectiles which seem to be multicolored and would thus require 2 sprites per projectile, adding up to 24? (although I see a couple of player projectile sprites disappear then, so maybe there is a shared pool for some player projectiles and the rest?)

Interesting Smile

Par lintweaker

Champion (411)

Portrait de lintweaker

01-02-2021, 13:33

lintweaker wrote:

Many games and demos use it. It can also be called 'line interrupt'.

http://map.grauw.nl/articles/split_guide.php

Grr, sorry guys. I did answer too soon. Somehow I missed the 'sprite' part of the question and read 'screen' :x

Par Daemos

Paragon (1951)

Portrait de Daemos

01-02-2021, 14:41

well a sprite split is very comparable to a screen split. You poll the lineint and then switch to another spritetable. If you change the lineint during the split you can do multiple splits per frame allowing many sprites in screen. Handling it nice and smoothly is another art though.

Par jltursan

Prophet (2532)

Portrait de jltursan

01-02-2021, 16:01

What happens when a sprite vertically lies between both screen areas?

Par Daemos

Paragon (1951)

Portrait de Daemos

01-02-2021, 16:06

引用:

What happens when a sprite vertically lies between both screen areas?

Varying from terrible to extremely bad Tongue Depending on how you handle it all good to white nasty lines or even broken sprites. Because the next line you start drawing the sprites the sprite that was in the other split is no longer being drawn. So you need to have copies of your spritedata and do the changes smoothly and that will cost you alot of CPU time.

Par jltursan

Prophet (2532)

Portrait de jltursan

01-02-2021, 19:19

Indeed the sprite splitting seems an arcane art in itself Shocked!

I wonder how the C64 sprites work this out...

Par aoineko

Master (163)

Portrait de aoineko

01-02-2021, 20:38

I made a sprite test program for my C library that uses screen-split to change the sprite display parameters: s_sprite.rom.
The screen-split is at the same time a very powerful tool that allows to get rid of some VDP constraints, but its use is quite limited because it is very specific.
Unless you think of a specific game to take advantage of these advantages, it is likely to be of little use to you.

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