From: ao950 AT FreeNet DOT Carleton DOT CA (Paul Derbyshire)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Allegro perspective-correct texture mapping
Date: 16 Mar 1997 11:38:01 GMT
Organization: The National Capital FreeNet
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Reply-To: ao950 AT FreeNet DOT Carleton DOT CA (Paul Derbyshire)
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To: djgpp AT delorie DOT com
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The heretic engine is clearly not the same as that in DOOM. For instance
look at the difference in HOM effects if you go off the map. (DOOM:
IDSPISPOPD. DOOM II, same engine: IDCLIP. Heretic: KITTY. Type the
appropriate code and walk through a wall.)

Doom's HOM effect flickers between three images because it uses a Mode X
triple buffer. (The game I'm writing also does and I have gotten HOMs
almost exactly like DOOM HOMs as a result of bugs in the background
routines that cause parts of the previous frame to persist.)

The no-flicker steady-HOM of Heretic means it uses a double-buffer system
with no page flip, i.e. draw onto BITMAP *buffer, then blit onto screen,
ad infinitum, which is slower but works in SVGA modes.

(Amazing what you can deduce about game engines from what happens when you
go places the manufacturer never intended and "break" the engine algorithm.)
--
    .*.  Where feelings are concerned, answers are rarely simple [GeneDeWeese]
 -()  <  When I go to the theater, I always go straight to the "bag and mix"
    `*'  bulk candy section...because variety is the spice of life... [me]
Paul Derbyshire ao950 AT freenet DOT carleton DOT ca, http://chat.carleton.ca/~pderbysh