From: bas AT merlin DOT ebicom DOT net
Message-Id: <2.2.32.19970316013323.0076202c@merlin.ebicom.net>
Mime-Version: 1.0
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Date: Sun, 16 Mar 1997 01:33:23 +0000
To: djgpp AT delorie DOT com
Subject: Re: Allegro perspective-correct texture mapping

At 03:02 PM 3/15/97 GMT, you wrote:
>
>
>Josh McDonald <os-dev AT effect DOT net DOT au> wrote in article
><01bc2ff7$739c9340$14621ecb AT homer DOT effect DOT net DOT au>...
>> 
>> HAHAHAHAHAHAHAHAA ROTFL...... How can we tell _everybody_ the truth
>> about doom so we don't get these messages anymore?
>> 
>> Doom does _not_ use raycasting, or raytracing. It draws polygons, 
>> which are sorted through a bsp. Sheesh..
>> 
>> -Josh
>
>	Actually, DooM looks at a table of which walls are displayed from where
>you are standing (it has a massive pre-calculated look up table), and then
>draws these walls by a simplified method of ray casting. It sends out one
>ray per a vertical display line (ie 320 in graphics mode 320x200, or 640 in
>the newer DooM95), which dictates how far away that part of the wall is.
>The texture is broken into vertical lines, and each vertical line is scaled
>individually to be drawn on the display at the size specified by the cast
>ray. You cannot look up and down because of the dependence on the lines
>being exactly vertical.
>
>		-Thomas
>
>
Well, I'm not to sure about all this but I do know you can look up and down
in Heretic which uses the doom engine


Bob Sayers
http://www2.ebicom.net/~bas/

"The speed of light sucks" -John Carmack