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From: zap@lysator.liu.se (Zap Andersson)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Fast 3d Graphics
Keywords: fast 3d optimizing assembly cycles
Message-ID: <558@lysator.liu.se>
Date: 4 Apr 91 12:10:36 GMT
Article-I.D.: lysator.558
References: <9529@star.cs.vu.nl> <1047@cbmger.UUCP>
Sender: news@isy.liu.se (Lord of the News)
Organization: Lysator Computer Club, Linkoping University, Sweden
Lines: 41

peterk@cbmger.UUCP (Peter Kittel GERMANY) writes:

>In article <9529@star.cs.vu.nl> mmblom@cs.vu.nl (Marc Blom) writes:
>>'m wondering how fast 3D graphics can really go. I've written some rotation
>>and perspective routines (in assembly) and profiling shows that 60 % of the
>>time is spend in my routine RotatePoint. This routine rotates 1 point around
>>all three axes in only about 900 cycles minimum and about 1100 cycles maximum.
Instead of rotation around one axis at the time, you may create a rotation
matrix, that rotates around all three axis simultaneously, with 9 multiplies.
The tecnique is picked up from any elementary cumputer graphics book, but
simply, it is:

NewX = OldX * XX + OldY * XY + OldZ * XZ
NewY = OldY * YX + OldY * YY + OldZ * YZ
New>Z = OldZ * ZX + OldY * ZY + OldZ * ZZ

where XX,XY,XZ,YX,YY,YZ,ZX,ZY,ZZ is your rotation matrix. You can think of
XX,XY,XZ as the (new) direction of the old X axis, and YX,YY,YZ as the
(new) direction of the old Y axis and so forth. You may easily build these
by taking the points:

  XX = 1, XY = 0, XZ = 0
 YX = 0, YY = 1, YZ = 00
 ZX = 0, ZY = 0, ZZ = 1
And rotate these using "your" method. Then Use these to rotate the other
points.

>-- 

>Best regards, Dr. Peter Kittel  // E-Mail to  \\  Only my personal opinions... 
>Commodore Frankfurt, Germany  \X/ {uunet|pyramid|rutgers}!cbmvax!cbmger!peterk
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--
* * * * * * * * * * * * * * * * *          (This rent for space)
* My signature is smaller than  * Be warned! The letter 'Z' is Copyright 1991
* yours!  - zap@lysator.liu.se  * by Zap Inc. So are the colors Red, Green and
* * * * * * * * * * * * * * * * * Greenish-yellow (Blue was taken by IBM)