AGA Sprite Palette

[Havie]

Help!

So I know that if I use AGA sprites with a dual playfield screen I can use 16+16 colours for the dual screens and as far as I know I can use a different 16 colours for the sprite palette but have no idea how to point the sprites to the correct palette?

I'm guessing it's something to do with Displaycontrols?

Thanks.

[Cobe]

Yup, I had the same question few years ago
http://eab.abime.net/showpost.php?p=...&postcount=129

[Daedalus]

BPLCON4 is used to select the colour banks used for sprites. Bits 0-3 select the 16-colour bank for odd numbered sprite channels & 16-colour sprites, and bits 4-7 set the bank for even numbered sprite channels. By default, they're both set to bank 1 (to match ECS), so the register will look like %00010001. Bank 2 is colours 32-47, bank 3 is 48-63 and so on.

[Havie]

Originally Posted by Daedalus

BPLCON4 is used to select the colour banks used for sprites. Bits 0-3 select the 16-colour bank for odd numbered sprite channels & 16-colour sprites, and bits 4-7 set the bank for even numbered sprite channels. By default, they're both set to bank 1 (to match ECS), so the register will look like %00010001. Bank 2 is colours 32-47, bank 3 is 48-63 and so on.

Thanks.

Are you saying I can have separate palettes for odd and even sprites - I thought they'd need to share the same palette?

And just to be clear, if I do:

Displaycontrols 0,0,0,%00100010

I will set the sprites to use palette entries 32-47?

Would I need to set up an initial 64 colour palette through the Initcopperlist?

And finally - how do you know this stuff? It's not clear in the manual and I couldn't find it on the Internet!

[Havie]

Originally Posted by Cobe

Yup, I had the same question few years ago
http://eab.abime.net/showpost.php?p=...&postcount=129

Yeah - found this but thought it was more to do with DP mode rather than sprites!

I have just about got a handle on most Amiga programming stuff now but palettes are surprisingly complex!

[Daedalus]

Originally Posted by Havie

Are you saying I can have separate palettes for odd and even sprites - I thought they'd need to share the same palette?

It depends on the setup. If you combine sprites to make 15-colour sprites, then they'll share the same palette (the one for odd sprite numbers). And OCS/ECS sprites always share the same palette from 16-31. But 3-colour sprites on AGA can use two separate banks for even and odd channels, with the result that every single sprite can use a different three colours.

And just to be clear, if I do:

Displaycontrols 0,0,0,%00100010

I will set the sprites to use palette entries 32-47?

Well, that's the idea, yes... But it's sadly a little more complicated than that. When you use DisplayControls command, the values for BPLCON2 and BPLCON4 are XORed with their default values. So to apply the value you want, you need to XOR it with the default so that it gets XORed back. For example:

Displaycontrols 0, 0, $c00, Xor($11, %00100010)

$11 is the default value listed in the manual (more on that below), and is the equivalent of the OCS/ECS mode, %00010001. You might find the hex values easier to think about - $22 is bank 2 for even and odd, for example, and $3F is bank 3 for even, bank 15 for odd.

Bizarrely, it appears that BPLCON3 values are directly applied instead of being XORed, so you might find you need to include the default as shown too.

Would I need to set up an initial 64 colour palette through the Initcopperlist?

Yes, you need to set the copperlist to have a 64-colour palette and your palette objects need to be large enough too. I'm not sure if 48 can be used, but it might be possible too, saving a few bytes of chip RAM

And finally - how do you know this stuff? It's not clear in the manual and I couldn't find it on the Internet!

It's a secret Yeah, the manual isn't that great. It does mention this is how it works, but neglects to give an example showing how to actually deal with the XOR thing, or that BPLCON3 doesn't appear to have this applied. The table from the manual also gives the bit function names of each of the registers, but doesn't give you anything other than "colour offset for even sprites" or something like that, which doesn't really tell you everything. I've explained it in a little more detail on AmigaCoding.com, but it still needs some more detail and examples.

Still, at this level we're dealing with the Amiga hardware directly and not so much with Blitz, so thankfully there are other resources for these details. One such site is amiga-dev.wikidot.com, which covers all the registers in the Amiga Hardware Manual, as well AGA registers that aren't covered in the Hardware Manual. On this page in particular it has some details of the BPLCON4 register, and the hardware page lists all the custom registers with information on each. It's a great website to have bookmarked!

[slademania]

Hi Havie,
In my game projects (that uses the DPF displays) I normally used the following
statement : Displayadjust Copnum, 0, $1c00, $00ee
where "Copnum" is the number of the copperlist initializated with the "InitCoplist" command and this gives me the following color palette:

Foreground playfield -> colours 0 to 15
Background playfield -> colours 16 to 31
Sprite color palette -> colours 240 to 255

I recognize that this command is a bit complicated to handle. I have been playing
with different values ??in bplcon3 and bplcon4 (following the documents on AGA
registers) and I have had quite strange results

[Cobe]

Originally Posted by Havie

Yeah - found this but thought it was more to do with DP mode rather than sprites!

I have just about got a handle on most Amiga programming stuff now but palettes are surprisingly complex!

Ah yes..
Looking at some other my code
Displayadjust Copnum, 0, $1c00, $0033
Would be for 16/16 dpf split and sprite colors from 32 to 48

[Daedalus]

Originally Posted by slademania

statement : Displayadjust Copnum, 0, $1c00, $00ee
where "Copnum" is the number of the copperlist initializated with the "InitCoplist" command and this gives me the following color palette:

Foreground playfield -> colours 0 to 15
Background playfield -> colours 16 to 31
Sprite color palette -> colours 240 to 255

I recognize that this command is a bit complicated to handle. I have been playing
with different values ??in bplcon3 and bplcon4 (following the documents on AGA
registers) and I have had quite strange results

If you don't XOR the values for BPLCON4, you'll get very strange results. $ee for sprite bank 15 works because it's XORed with the default of $11, resulting in $ff (bank 15 for both even and odd sprites).

Originally Posted by Cobe

Ah yes..
Looking at some other my code
Displayadjust Copnum, 0, $1c00, $0033
Would be for 16/16 dpf split and sprite colors from 32 to 48

And the same here - XOR $33 with $11 and you get $22 - bank 2, which is 32-47.

[Havie]

Thanks guys - will implement in my SF2 demo code!

[Havie]

Thanks to all your help, I got it working. You guys are stars!

http://eab.abime.net/showpost.php?p=...&postcount=398

[Havie]

Now added an additional background that shows floor effect better:

https://eab.abime.net/zone/Streetfigher2test.adf

You can also chose background with 1 or 2 buttons.

Would like to add a few more moves and get Chunli animated too just too see!