To:	chambersb AT juno DOT com
Cc:	djgpp AT delorie DOT com
Subject:	Re: Allegro perspective-correct texture mapping)
Message-ID:	<19970317.171229.7391.0.fwec@juno.com>
References:	<5fg3s0$hob$1 AT troll DOT powertech DOT no> <331F047A DOT 271F AT cam DOT org> <01bc2ff7$739c9340$14621ecb AT homer DOT effect DOT net DOT au>
From:	fwec AT juno DOT com (Mark T Logan)
Date:	Mon, 17 Mar 1997 17:14:18 EST

On Sun, 16 Mar 1997 00:14:42 EST chambersb AT juno DOT com (Benjamin D Chambers)
writes:
>
>On 15 Mar 1997 15:02:00 GMT "Thomas Harte" <*T DOT Harte AT btinternet DOT com> 
>writes:
>Has anyone actually asked the people at Id?
>Personally, I find the explanation that they used BSP's a lot more 
>plausible than using the raycasting engine (and, yes, we know of the 
>simplified version you mentioned).
>It occured to me that all this bickering over it could be done away 
>with just by asking the guys who made it, but I don't know if this has 
>been done.  Has anyone?

Well, I can't speak for Id, but I have some very compelling evidence to
present.  DEU 5.1
has a bsp building function in it.  (look under nodes.c if you have the
source).  Why would
DEU build a bsp tree if doom didn't use one?

However, a doom level also has a block map, which is a set of blocks of
level space, and
a list of walls that can be seen from that particular block. CMIIW.  I
believe that is where
the raytracing thing came from.  I for one suspect that doom walks the
bsptree, and when
it needs to draw a polygon, it does so by casting rays along the length
of it.  I think I will 
ask John Carmack if he will comment on the situation.  (I know I've got
his e-mail address
around here somewhere.)  Id is pretty generous with there technology, so
I think there's
a decent chance he will respond.

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