Subject: Re: Bitplane moving
From: Acid Software <[email-masked]>
To: Dave Cole <[email-masked]>
Cc: Blitz <[email-masked]>
Date: Thu, 18 Aug 1994 18:21:10 +1200 (NZST)

Move individual bitplanes?

If you are going to ask such bizarre questions a little outline of what 
you are trying to acheive may help us offer advise.

Two ways spring to mind..

Use bitplanesbitmap to isolate the single bitmap and call scroll, if it 
is only 1 bitplane scroll will be nice and fast. If I had a sixbitplane 
bitmap as bitmap 0 I would go...

bitplanesbitmap 0,1,2^n ;n is the bitplane I want to scroll

then anytime I wanted to scroll it:

use bitmap 1:scroll ....

The other way would be to hit the bitplane object in memory, make sure it 
is not the first bitplane you want to use and do the following:

ad.l=addr bitmap(0)+8+n*4 ;where n is the bitplane (not 0!)
cpos.l=peek.l(ad)         ;current position of plane in memory

poke.l ad,cpos+int(x/16)*2+y*bitplanewidth

Next time you do a show the bitplane we just hit will be offset by x,y, 
note however you can only scroll in x in multiples of 16, so this method 
sucks.

Last method would be using the 64 wide sprites as an extra playfield and 
writing som machine code routines to display data in them. I'm not going 
to write them.

Love and flowers,

Simon