From: rjc@hal.gnu.ai.mit.edu (Ray)
Newsgroups: comp.sys.amiga.advocacy
Subject: Re: Unreal demo!
Date: 3 Sep 92 20:44:08 GMT
Organization: /etc/organization


In article <1992Sep3.184507.22590@ctr.columbia.edu> jerry@connection.prospect.com (Jerry Shekhel) writes:
>rjc@hal.gnu.ai.mit.edu (Ray) writes:
>>
>>but Unreal is no match for demos
>>like Hardwired, Unreal is pathetic in comparison.
>>
>
>Unreal is also one of the first few PC EuroDemos.  Give 'em time.

   They've had since 1985.  Times up! The reason it has taken so
long is VGA provides none of the facilities for doing good demos.
No blitter, therefore, code your own fast line draw/poly filler, 
your own multisource logical blit routine. 
No sprites, therefore, code your own sprite simulator. 
No copper, therefore, attempt, through hackery, to try beam
synchonized effects (which don't work on all VGA cards. For instance, faked 
copper effects cause my friend's VGA to display garbled dots all over the 
screen.). 
No playfields, therefore, fake playfields using blits.

    All of this has to be coded and somehow made quick enough to
work through the VGA bottleneck. (the "special" trick here is
to do all your work in fast ram, then copy it to the display)

     I predict you won't see A500 class demos until the 586 and
localbus video are standard.  Talk about throwing megahardware
at a problem.

    VGA's paradigm is incompatible with visual effect demos.

>>
>>The fact that it takes
>>a 486 to get any real demo performance out of SVGA shows the
>>efficiency of using stupid frame buffers for something as complex
>>as a demo.
>>
>
>Unreal runs at full speed on my 386.

    Does it run on a 286? 386sx?  Hardwired runs way smoother on my 500.

>>
>>I know from personal experience how hard it is to
>>do a simple half-screen sin-wave scroller on the PC (even using
>>the so-called special tricks like mode 13h)
>>
>
>I can see already how much you know.  Mode 13h is not a special trick; it's
>just the standard VGA 320x200 256-color graphics mode.  The 8-bit planar
>modes like X and Y are the special tricks.

   That's why I said "so-called".  You should stick to reading 
Dr Dobbs, and PC "how to code demos" text files. Mode 13h is
described as "the special trick to doing demos and games".
I can already see how much you know about coding sine scrollers.
Planar modes actually make it harder to do a color sine scroller.

  There are no "special tricks" to be done on VGA like there is on
the Amiga or C64.   Amiga Demos ride a very fine line of what is 
"legal" on the hardware.  Many of them poke registers they shouldn't, use
microsecond cpu-timing loops, do things to the hardware that cause wierd
side effects.   None of these things can be done on the PC without
being incompatible unless written for a specific VGA chipset, cache,
and CPU machine.   Just try synching multiple blits down to
a single cpu _cycle_ while staying synched with the raster beam
on a 386/VGA.  Amiga demos do this all the time. All one has to do
is try and run one in NTSC and you will fine it locking up or crashing
because of the small timing differences. (or locking up on a 3000)

  It's been 6 years since the first Eurodemo scrollers on the Amiga.
The PC finally gets one demo that's worth anything and you tell
me to be patient? Will I have to wait another 6 years until
I finally see plasma bob effects on the PC? No thank you.

  Face it, the PC just isn't suited for demos.  If and when the PC
finally does get a demo similar to Hardwired, I'll just claim
it's too little, too late, and to much extra cpu power for something
that is done easily on a 68000.

   I'm happy with Linux on my PC, I can't complain about free unix,
but an Amiga, the PC will never be. The hardware doesn't have the
"neato" factor. I can't wait for the first AA chipset demos.

>--
>+-------------------+-----------------------+--------------------------------+
>| Jerry J. Shekhel  | Molecular Simulations | Time just fades the pages      |
>| Drummers do it... | Inc.  Waltham, MA USA | in my book of memories.        |
>|    ... In rhythm! |     (617) 890-2888    |              -- Guns N' Roses  |
>+-------------------+-----------------------+--------------------------------+
>|           ...! [ princeton mit-eddie bu sunne ] !polygen!jerry             |
>|                            jerry@polygen.com                               |
>+----------------------------------------------------------------------------+
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