Ultimate Amiga

Network Boards => AMOS Language Discussion => AMOS Factory => AMOS The Creator Forum => Topic started by: KevG on October 11, 2013, 09:55:04 AM

Title: Sprites behind back playfield in dual playfield mode
Post by: KevG on October 11, 2013, 09:55:04 AM

Hi folks

Its a long shot I know but does anyone have any code that allows you to display hardware sprites in different planes in dual playfield mode?

I know that it is possible to do this with the AMCAF extension but that is for AMOS Pro. I need a hack or something similar for AMOS 1.3

Any help would be appreciated.

Title: Re: Sprites behind back playfield in dual playfield mode
Post by: Lonewolf10 on November 14, 2013, 09:40:50 PM

It's difficult because AMOS is constantly changing the copperlist. There is a register used to set sprite priorities (BPLCON2). See here for info:

http://amigadev.elowar.com/read/ADCD_2.1/Hardware_Manual_guide/node0022.html (http://amigadev.elowar.com/read/ADCD_2.1/Hardware_Manual_guide/node0022.html)

BPLCON2 is at $DFF104. You can only write to this register. Attempting to read from it will probably results in abnormal behaviour or AMOS crashing. Writing to (Poking) it in AMOS may also cause the Amiga to crash.

You can try that, but I have a feeling that AMOS probably sets BPLCON2 at the start of the copperlist - which is executed every VBL.


Alternatively, you can create your own copperlist in AMOS, but then you'd have to do all the hard work with the hardware sprites and AMOS drawing/screen-based commands would no longer work reliably, if it all.

Title: Re: Sprites behind back playfield in dual playfield mode
Post by: KevG on November 23, 2013, 10:03:01 PM

Thanks Lonewolf10.

I'll look into it further and if I get anywhere I'll post my findings here.

Cheers.