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Running Games and Apps.

[Development] Sprite Reuse + Priority Queue

Olle Haerstedt

Posts 102
25 Mar 2020 14:38


How about implementing sprite reuse together with a priority queue, so that if too many sprites overlap horizontally, they will take turn being visible (leading to a flickering, which is the trade-off). Anyone know of such a system? Compare with e.g. NES games and their flickering when too much happens on the screen.

Use-case could be an RTS engine with troops, where each troop is a sprite no matter the total number.


Gunnar von Boehn
(Apollo Team Member)
Posts 4795
25 Mar 2020 18:08


Let us give a brief over view about Amiga Sprites features.

The Amiga has 8 sprite channels.
Each Sprite channel can display many sprites as long as they are below each other on the screen.
For example if your have a game like 1942 then you could with one sprite channel display many bullets flying up.
If you use a sprite channel you could even display 100 small stars with just one Sprite channel.

This means which clever usage of the Sprite Channel a game can display quite a lot of Sprites.

There are limitations. You can only show 8 Sprites in the same row - unless you use tricks with the Copper. The Copper could in theory increase this.




Olle Haerstedt

Posts 102
25 Mar 2020 20:25


Hi!
 
  8 sprite channels, so 8 sprites on each horizontal line, 256 lines, that gives 2048 sprites in total if the sprite is 1 px high. You saying this is possible? What would such a copperlist look like? oO
 
  Any link to copper increasing number of sprites possible on one row?


Samuel Crow

Posts 387
25 Mar 2020 20:34


Horizontally muxed sprites must use the same image data.  The data is fetched once in the left border of the screen and is typically used for repeating backdrops.  SAGA has a special mode that allows horizontal clipping to be turned off which is more efficient than using the copper to move sprites right x pixels after being displayed the first time.


Olle Haerstedt

Posts 102
25 Mar 2020 20:59


Samuel Crow wrote:

Horizontally muxed sprites must use the same image data.  The data is fetched once in the left border of the screen and is typically used for repeating backdrops.  SAGA has a special mode that allows horizontal clipping to be turned off which is more efficient than using the copper to move sprites right x pixels after being displayed the first time.

Cool. Sounds like a blog post waiting to happen. :)


Gunnar von Boehn
(Apollo Team Member)
Posts 4795
25 Mar 2020 21:28


Olle Haerstedt wrote:

Hi!
   
8 sprite channels, so 8 sprites on each horizontal line, 256 lines, that gives 2048 sprites in total if the sprite is 1 px high. You saying this is possible? What would such a copperlist look like?

For vertical Sprite Re-use you not need any copper list.
The Sprite Channel DMA can this by itself.
The DMA "works" like a playlist.
Between each Sprite,re-used Sprite will be 1 transparent row.
This means 256 = 128 Sprite per Channel max.
128*8 = max 1024 Stars on Screen
:-)
 
You need a Copperlist trick only to re-use the Sprite horizontally.
SAGA adds a new Register-BIT, which allows horizontal Re-used without Copper even.


Olle Haerstedt

Posts 102
25 Mar 2020 23:00


Gunnar von Boehn wrote:

Olle Haerstedt wrote:

  Hi!
   
  8 sprite channels, so 8 sprites on each horizontal line, 256 lines, that gives 2048 sprites in total if the sprite is 1 px high. You saying this is possible? What would such a copperlist look like?
 

  For vertical Sprite Re-use you not need any copper list.
  The Sprite Channel DMA can this by itself.
  The DMA "works" like a playlist.
  Between each Sprite,re-used Sprite will be 1 transparent row.
  This means 256 = 128 Sprite per Channel max.
  128*8 = max 1024 Stars on Screen
  :-)
 
  You need a Copperlist trick only to re-use the Sprite horizontally.
  SAGA adds a new Register-BIT, which allows horizontal Re-used without Copper even.

I definitely want to try this.


Olle Haerstedt

Posts 102
26 Mar 2020 19:36


Some guy made a sprite engine with 94 sprites moving randomly. No source code or explanation on how. EXTERNAL LINK

posts 8