From: bloc1469@ee.ee.uwm.edu (Gregory R. Block)
Newsgroups: comp.sys.amiga.advocacy
Subject: Re: **** A1200 Info **** (200+ lines)
Date: 8 Nov 1992 18:47:06 GMT
Organization: Electrical Engineering Dept. University of Wisconsin - Milwaukee
NNTP-Posting-Host: 129.89.2.33

In article <1992Nov7.174103.20817@news.th-darmstadt.de> wallmann@backus.pu.informatik.th-darmstadt.de (Natuerlich!) writes:
>So when comparing screenmodes to establish some 'bogus' superiority of the 
>AA chipset, using HAM colors is bullshit. A better metric is Mbytes/s on 
>the graphic hardware. How many RAM bytes are converted by the graphics 
>hardware each second. My original remarks on the cheesiness
>of HAM stems from someone comparing A1200 screenmodes to the Falcon030.

>Take at least a minor stab at comprehending, what I or the previous poster
>(Hi James) are trying to say.

Stab.

>Chuckle. This is only true for the borderline case, where your data is
>the size of the complete screen.

Some clever programming, not that you're capable of it, shows that
it's perfectly possible.  If you're still not sure, then maybe you
should take a look at some of the GAMES that used it.

It would be a mistake to assume that it's not possible.  Don't make it.

>It's just not of any use. Judging from your post you have a very naive
>view of what HAM is and how you access/change pixel values in a HAM
>screen. If you want to color a pixel in plain red at coordinates x/y you
>must know the color of the pixel at 0/y then you have to calculate all the
>pixel colors between 0-(x-1), in order to get the color you want to modify.

Unless, of course, you've got the color you want sitting in one of the
64 available color registers.

>(#1#) now you can modify your value and then you have to adjust the value
>of pixel x+1 so that it remains near the same color. Since you can't change to
>any color in HAM (not a RAP) you might not get the red you want but something
>close. 

Again.  There are 64 color registers in which to store your most
oft-used stuff.  And do remember that the Amiga does have sprites.
Using VSPRITES for your stuff under 3.0 is perfectly possible.  You
can have 8 per scanline, no more.  However, those sprites are "reusable".

You could also use BOBs.  You'd have to use the base 64-color
registers for the background and make your BOB's in ham surrounded by
one of the base 64 colors on one side.  But careful planning of your
graphics could make that indistinguishable.  Also, remember, that with
multiple viewports, you can set up multiple resolutions onscreen.  If
all you need is the center 2/3 of the screen in HAM, that's all you
really have to use.  You simply pop 256-color lores/hires/whatever
viewports along with that ham screen, and decide what you want where.

>Assume you want to 'blit' a little shape from HAM to HAM. Can you just 
>use a memory copy with the blitter? No because the color information of
>the HAM pixels are only valid at this position. Hence you must, convert
>the HAM pixels into color values, and convert them back into HAM pixels
>at the destination.

That's one way, yes.  Like I said, there are some tricky things you
can do.  If you just need to move "blocks" of things, think about what
you have to do ahead of time, and plan.  Invisibly "tile" your screens
with base color values on the left side.  Then, you're able to swap
anything you like with anything else, as long as they're block-sized.

Or, if you prefer, keep "tables" of color values out.  That costs
calculation times, yes.  However, with fast ram, it could end up being
faster than the Falcon's truecolor mode.  The processor could be
calculating what it needs to do in fast ram, moving the result into
chip.  Since the TC mode is going to be moving the data anyways in
that situation, you're only losing calculation time.  Since the TC
mode takes more bandwidth than an 8-bit mode does, it's possible to
get away with it.

With fast ram.

Theoretically.

>In laymans terms, it is comparable to editing a plain ASCII file (RAP-edit)
>and lossily editing a compressed ASCII file (HAM-edit). What would you
>rather do ?

Which do you think.  I'm not slamming the truecolor mode.  I'm just
saying that the HAM mode deserves more credit than you give it.  And
if used creatively, it has benefits over RAP.  Game companies have
known that for a long time.

>This IS a speed penalty. Compare to that the beauty of plotting a 
>pixel in "Falcon TrueColor" mode;

I'd say "ease" is a better word.  C is nice, but I'd never give it
"beauty".

>As to the point, "it's clear that you haven't used an Amiga before".
>Not TRUE!! I played on an Amiga with friends (KICK-OFF) for an estimated
>48 hours total. (har)

I'd venture to say that 48 hours with one game on what is probably a
1.3 AmigaDos game would give you a poor idea of the Amiga's
capabilities.

>P.S. Obvious improv. like hash-tables left out.

What a good idea.  :)

Greg

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