| From: | Paul Hill |
| Date: | 5 Jul 2000 at 22:24:20 |
| Subject: | Re: Gfx cards + AGA |
On 05-Jul-00 18:07:33, Bart King wrote:
>Matt Sealey <matt@kittycat.co.uk> wrote:
>[scrolling + layers]
>> Poorly implemented how?
>While I did not program the AGA chip set,
I can tell.
>What Commodore did was to develop a graphics chip set which was
>state-of-the-art at the time. It does amazing things if
>a) You can figure it all out; don't forget that Commodore never actually
>got around to releasing full-blown AGA documentation.
There's a 6 year old AGA guide on Aminet.
>b) You keep resolutions television compatible
>c) You bypass all system routines and program (hack) AGA direct.
>Although AGA was not developed to be fixed at a specific resolution (that's
>the beauty of it), the way things like layers and scrolling give poor
>performance when resolutions increase.
AGA has very powerfull support for scrolling. You can scroll the screen in
*less than* 1 pixel increments (35ns or 1 shres pixel). Even High-res
screens are as fast. And because of the copper (ever seen one of these on
a gfx card?) you can scroll different areas at different speeds with ease.
>Take for example a 320x256 screen and a 1024x768 screen - one four times
>the size of the other. Memory issues aside, scrolling both screens 32
>pixels to the left, would require the Blitter (not CPU) to shift all the
>pixels.
No it doesn't. You can pan the video 'window' anywhere through the 2Mb
of chip ram by changing a couple of registers. Admittingly you need to
draw the new data at the edges but that's only a small amount.
>BitMap's on the Amiga are planar. This is a special format used by Amiga
>and only Amiga
Several platforms support planular gfx. Even VGA.
>which allows shortcuts to be taken on how the graphics
>chip sets figure out what should be passed to video out. Such shortcuts
>include "masking" pixels in with each other to give the appearance of one
>color for one or more pixels. This masking is actually a visual effect,
>and works if the resolution and frame rate/frequency match up with the
>video display.
What have you been smoking? (and can I have some :-)
>The Blitter has its work cut out to shift 761,856 (992x768) pixels to the
>left, where as it'll manage 73,728 (288x256) with some ease. If the
>Blitter does not complete the scrolling operation before the next video
>beam sweep, you'll get the effect of a blurred scrolling, which can look
>cool or shit depending on how you look at it.
It's an old problem. But when have you ever seen it in any Amiga game?
Don't forget that while the blitter is making its blits you can do other
things with the CPU.
>This method of scrolling has long been surpassed with special components on
>graphics devices to handle scrolling which can achieve fast scrolling in
>graphics memory at blistering speeds.
Crap. You can't get any better or easier than AGA when it comes to
scrolling. It takes just a couple of longword writes by the CPU to scroll
the screen through x or y.
AGA may be crap at nice hi-res displays but for scrolling games it can't be
easily beat.
------------------------------------------------------------------------
Where do sports heroes like Derek Jeter, Mia Hamm,
Vince Carter and Peyton Manning hang out? Where else?
Click now and find �em all here!
http://click.egroups.com/1/6211/4/_/468125/_/962837624/
------------------------------------------------------------------------
Quote carefully and read all ADMIN:README mails