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From: Ordania-DM@cup.portal.com (Charles K Hughes)
Newsgroups: rec.games.programmer,comp.os.msdos.programmer,comp.graphics
Subject: Re: Need hard core help doing some 3d optimizations
Message-ID: <41220@cup.portal.com>
Date: 13 Apr 91 01:57:18 GMT
References: <27979@uflorida.cis.ufl.EDU>
Organization: The Portal System (TM)
Lines: 62


  Does this discussion really need to be in 3 newsgroups?

Brian writes:
>
>I just ran Turbo Profiler on some code of mine, and it looks like roughly
>90% of my CPU time is being shoved into one function.  Any help on the

  I don't know what the rest of your program looks like, but I don't think
this code should take up 90% of it.  
  (Before following my mediocre suggestions, follow the others that have been
posted - TSR removal, use Ints, etc.)

>optimizations would be really appreciated.
>
>E-mail would be preferred, however posts are fine too.
>
>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;

   Change these last two to:
    yes_a_temp=AngPerspFactor/WorldZ;
    *DisplayX=yes_a_temp*WorldX
    *DisplayY=yes_a_temp*WorldY

   Division costs a lot more than multiplication or storage.

>}
>
>AngPerspFactor is a float, as are the assorted factors.  I have already
>used a COS and SIN lookup table in another part of the module to expedite
>things, but this is really slowing things down considerably.
>
>Any help is appreciated.
>
>Brian
>
>   

  Now, for independend thoughts that don't quite fit into the program...
There are formulas for transforming the equations you have above.
Calculus and trig books should have them.


Good luck.
Charles_K_Hughes@cup.portal.com