From: broehl@sunee.waterloo.edu (Bernie Roehl)
Subject: TECH: Re: Wolf 3d annoys me (CROSSPOSTED!).
Date: Tue, 12 May 1992 15:09:14 GMT
Message-ID: <1992May12.150914.13846@watserv1.waterloo.edu>
Organization: University of Waterloo



[MOD'S NOTE:  This was crossposted to rec.games.misc, as well as to sci.
virtual-worlds.  I delete multiple newsgroups so that the mailer won't
pump out messages all over the universe. -- B.J.]


NOTE THE CROSSPOSTING!  This article is (probably) of interest to both groups;
followups should (probably) be directed to only one of the two.

In article <1992May11.190117.13434@galileo.cc.rochester.edu> writes:

>   The only reason why W3D is faster than UW is because they only have to
>texture map onto square planes, have only one level (ground level), don't
>have to texture ceilings and floors, and don't have to handle diminishing
>light.  If Apogee did all that, you would see a slowdown.

Agreed.  I know a little something about 3D graphics (I'm a co-author, with
Dave Stampe, of the REND386 libraries).

Why Wolfenstein 3D is so fast, even on a slow machine:

Wolf 3D is basically a 2-D game with a perspective view.  All coordinates
are two-dimensional; you can't look up, you can't look down, there are no
stairs or ramps or cliffs or waterfalls the way there are in Underworld.
All walls are exactly the same height.

All polygons are axis-aligned rectangles.  The "ceiling" and "floor" are
done by just clearing the top half of the screen to one color and the bottom
half to another.  There are no real 3-D objects (Underworld has several:
benches, Ankhs, barrels... Wolfenstein's objects are all just scaled bitmaps).

By simplifying the environment so much, Wolfenstein gains several advantages
that lead to increased speed:

   - only have to do 2D transforms, not 3D
   - only have to transform two vertices per poly, not 4 as in Underworld
   - backface removal is done with a compare instead of a vector dot product
   - "collision detection" is trivial
   - texturing is much, much easier (not really harder than scaled bitmaps)

However, Underworld gives you a much richer, more complex world to play
around in.  Being able to jump across chasms, swim along underground rivers,
and go racing down stairs to avoid whatever's after you is (to me) much
more exciting than running around a 2-D plane shooting dogs and German
soldiers.

Underworlds's still not completely general (you can look up and down, but
can't tilt your head over onto your shoulder, for example) and their
texturing shows considerable distortion when you look up or down.  They also
have the odd visibility error (but then again, who doesn't?)

>Also, the game [Wolfenstein] does wear thin after the first few times.

Agreed.  I've played Wolfenstein for 15 minutes here and there (to avoid
the headaches and nausea -- I get them too), but I've spent hours and hours
in Underworld.

However, both games are a tribute to the work of their programmers.  It's
interesting that in the last 6 months there's been an explosion of 3D
software for low-end machines.  Wolfenstein, Underworld, Virtual Reality
Studio, the Superscape stuff, REND386, the UltraForce people, Canon...
I suspect the reason it took so long is that no one really believed it was
possible to get the kind of speed we're seeing; as soon as someone did it,
everyone else realized it could be done.

Incidentally... demos of VRS, Superscape, REND386 and UltraForce are all
available on sunee.uwaterloo.ca in the pub/vr directory.  You can get
Wolfenstein 3D from there as well, but we'd much prefer you get it from
ftp.ulowell.edu (which is bound to have a more recent version).  Remember to
transfer .ZIP files in binary mode!  Also note that our site is only connected
over a (very busy!) 56kb link, so please only transfer large files
during the late evening or on weekends.

Sorry, I don't have time to email files to anybody; send email to
ftpmail@decwrl.dec.com with the word "help" in the body (not the subject line)
to get details on retrieving files by email if you have no ftp capability.

(An aside to the folks from Canon: if you have a demo you'd like to share with
the world, let me know via email and I'll be happy to add it).

-- 
	Bernie Roehl, University of Waterloo Electrical Engineering Dept
	Mail: broehl@sunee.waterloo.edu OR broehl@sunee.UWaterloo.ca
	BangPath: uunet!watmath!sunee!broehl
	Voice:  (519) 885-1211 x 2607 [work]