Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!motcsd!xdos!doug
From: doug@xdos.UUCP (Doug Merritt)
Newsgroups: comp.sys.amiga
Subject: Re: 4096 colors in HIRES
Summary: How about leaving time for multitasking, w/ only 8 colors/scanline?
Message-ID: <421@xdos.UUCP>
Date: 6 Jul 89 15:19:33 GMT
References: <20069@cup.portal.com> <409@xdos.UUCP> <20112@cup.portal.com> <412@xdos.UUCP> <1166@atanasoff.cs.iastate.edu> <8721@thorin.cs.unc.edu>
Reply-To: doug@xdos.UUCP (Doug Merritt)
Distribution: usa
Organization: Hunter Systems, Mountain View CA (Silicon Valley)
Lines: 45

In article <8721@thorin.cs.unc.edu> cullip@unc.cs.unc.edu (Timothy Cullip) writes:
>Actually the 4096 color mode in HIRES can be quite useful.  I have recently
>modified a ray tracer I wrote that used to use 320x400 HAM to now also use
>640x400 HIRES with the ability to change the color registers every scanline.
>I have found that with 4 bitplanes the bus is too busy during the scanline
>to get any color registers changed through copper instruction, but during
>horizontal blank I can easily change 13 of the 16 registers.  You end up

That's interesting. So there's time for a lot more color register loads
than I'd (mis-)remembered.

There would seem to be some interesting tradeoffs involved here. The
implication is that there isn't any bandwidth left for a 14th register
change, of course, nor for that matter, left for doing anything else,
either.

>  I even have it
>behaving quite well under Intuition (but screen drags are very slow!).  

Right, the only time the processor can get anything done is during vertical
retrace. Perhaps it would be a good idea to leave some more time slots
open so that *some* things can still happen during horizontal retrace.

For instance, if you restricted it to 8 color register changes per scan
line, then presumably system response would be much snappier, and background
tasks would be able to run sometimes, yet you'd still have lots of colors
to play with (one complete palette switch every two scan lines).

>The limit of 16 colors per scan line can be somewhat of a problem in a ray
>tracer, but for the most part my pictures turn out much nicer looking than
>the old 320x400 HAM pictures I was generating.

Yes. And although 8 colors/scanline is still more limited than 13/scanline,
I'm sure it'd still look nicer than HAM. And consider how much more effective
it would be to show off the Amiga to someone if you could still get
reasonable system response even while displaying a really nice image.

I don't think that dealers, for instance, would ever show the 13/scanline
images, because it'd impact performance so much.

And, hmmmmm, what about playing background music?
	Doug
-- 
Doug Merritt		{pyramid,apple}!xdos!doug
Member, Crusaders for a Better Tomorrow		Professional Wildeyed Visionary