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From: rcb@shaman.cc.ncsu.edu (Randy Buckland)
Newsgroups: rec.games.programmer,comp.os.msdos.programmer,comp.graphics
Subject: Re: Need hard core help doing some 3d optimizations
Message-ID: <rcb.671459927@shaman.cc.ncsu.edu>
Date: 12 Apr 91 12:38:47 GMT
References: <27979@uflorida.cis.ufl.EDU>
Sender: news@ncsu.edu (USENET News System)
Organization: North Carolina State University
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jdb@reef.cis.ufl.edu (Brian K. W. Hook) writes:
>void Calc3D ( int WorldX, int WorldY, int WorldZ,
>	      int MX, int MY, int MZ,
>	      int *DisplayX, int *DisplayY)
>{
>float xa, ya, za;

>   WorldX=-WorldX;
>   xa=_yawCosFactor*WorldX-_yawSinFactor*WorldZ;
>   za=_yawSinFactor*WorldX+_yawCosFactor*WorldZ;
>   WorldX=_rollCosFactor*xa+_rollSinFactor*WY;
>   ya=_rollCosFactor*WorldY-_rollSinFactor*xa;
>   WorldZ=_pitchCosFactor*za-_pitchSinFactor*ya;
>   WorldY=_pitchSinFactor*za+_pitchCosFactor*ya;
>   WorldX+=MX;
>   WorldY+=MY;
>   WorldZ+=MZ;
>   *DisplayX=AngPerspFactor*WorldX/WorldZ;
>   *DisplayY=AngPerspFactor*WorldY/WorldZ;
>}

Try this

Store your cos/sin values as (int)(cos(angle)*1024)
Then do the matrix multiply as

	c(0,0) = (a(0,0)*b(0,0) + a(0,1)*b(1,0) 
		+ a(0,2)*b(2,0) + (a(0,3)*b(3,0)) >> 10;

where a is your initial 4x4 coordinate matrix and b is your translation
matrix that is precomputed. ALL values in the b matrix should be integers
that are 1024 times their proper values while a is an integer matrix with
the proper values and c is an integer matrix. This results in 4
integer multiplies, 3 integer adds and 1 shift (the reason for 1024 instead
of 1000 scale factor) No floating point at all.

Also, try to determine if you are really rotating about all 3 axes. If not,
you can drastically simplify the computations and increase the speed.

--
Randy Buckland						"It's hard to work
North Carolina State University				in a group when you're
randy@ncsu.edu (919) 737-2517				omnipotent"	-- Q