From:	Vic <tudor AT cam DOT org>
Newsgroups:	comp.os.msdos.djgpp
Subject:	ANOUNCE: clipping tutorial+code
Date:	Sat, 12 Jul 1997 21:30:11 -0400
Organization:	Communications Accesibles Montreal
Lines:	31
Message-ID:	<33C82FA3.121E@cam.org>
Reply-To:	tudor AT cam DOT org
NNTP-Posting-Host:	dynppp-85.hip.cam.org
Mime-Version:	1.0
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

There was a discussion on rec.games.programming about 3D basic
tutorials.It seems there is a lack of info about clipping so I wrote
one. It targets newbies in 3D coding that want to learn to do the
clipping stuff. The code is fully functional, in C (no ASM).
it's at http://www.cam.org/~tudor/cliptut.zip

Some speed related stuff:
the function that gets the equation of a plane:
GCC full optimisations: around 800 000-900 000 per second.
GCC pentium optimisations: around 1 000 000 per second.
(I know this function is not used in the actual clipping code but it
might be useful in, let's say, a Z buffering system)

the function that gets the intersection of a line with a plane:
GCC full optimisations: around 500 000 per second.
GCC pentium optimisations: around 600 000 per second.

the function that clips a poly with a plane (triangle):
GCC full optimisations: around 130 000-140 000 per second.
GCC pentium optimisations: the same.
Of course the number of those done per second decreases with the number
of points in your poly... for 6 it gets down to 60 000-70 000

the function that clips a poly to the frustum (triangle):
GCC full optimisations: around 25 000-30 000 per second.
GCC pentium optimisations: the same.

what do you think? How fast are they? Any ways to optimise it further?
(while keeping it in C only)
TIA,
Vic.

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