Path: chuka.playstation.co.uk!news
From: "Andrew Murray" <sckoobs@yahoo.com>
Newsgroups: scee.yaroze.freetalk.english
Subject: Re: Sine & Cosine Lookup Tables
Date: Wed, 11 Dec 2002 11:33:45 -0000
Organization: PlayStation Net Yaroze (SCEE)
Lines: 111
Message-ID: <at78bj$5s02@www.netyaroze-europe.com>
References: <at24hi$4654@www.netyaroze-europe.com> <at27a1$4655@www.netyaroze-europe.com> <at2i1k$4657@www.netyaroze-europe.com> <at2v55$46510@www.netyaroze-europe.com> <at58g9$5s01@www.netyaroze-europe.com>
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Thanks guys, if I do use it I'll be sure to put in the credit. I have to
figure out how it works first :)

Andrew.

"Matt Verran" <matt@hermitgames.com> wrote in message
news:at58g9$5s01@www.netyaroze-europe.com...
> Jon Prestidge has kindly passed on this code, remember to thank him if you
> use it!
>
> long auto_arc_tan( long v_dx, long v_dy )
>    {
>    // V1
>    //
>    // (C) Jon Prestidge, 1998.
>    //
>    long grad, ang, deg, abs_dx, abs_dy, half;
>
>    abs_dx = v_dx;
>    if ( abs_dx < 0 ) abs_dx *= -1;
>    abs_dy = v_dy;
>    if ( abs_dy < 0 ) abs_dy *= -1;
>
>    // find the gradient between 0 and one (or 0 and 4096 in this
> impelmentation)....
>    if ( abs_dy <= abs_dx )
>       {
>       if ( abs_dx == 0 )
>
>
>          // exact angle can be returned... also this prevents divide by 0
> error...
>          if ( v_dy >= 0 )
>             return 0;
>          else
>             return 2048;
>          }
>       grad = abs_dy;
>       grad <<= 12;
>       grad /= abs_dx;
>       half = 1;
>       }
>    else
>       {
>       if ( abs_dy == 0 )
>
>
>          // exact angle can be returned... also this prevents divide by 0
> error...
>          if ( v_dx >= 0 )
>             return 1024;
>          else
>             return 3072;
>          }
>       grad = abs_dx;
>       grad <<= 12;
>       grad /= abs_dy;
>       half = 0;
>       }
>
>    ang = ( grad * 2409 ) >> 12;
>    ang *= 4096 - ang;
>    ang += grad * 3097;
>    ang >>= 15;
>
>    deg = ang * 90 / 1024;
>
>    if ( v_dx >= 0 )
>       {
>       if ( v_dy >= 0 )
>          {
>          if ( half ) ang = 1024 - ang;
>          }
>       else
>          {
>          if ( half )
>             ang += 1024;
>          else
>             ang = 2048 - ang;
>          }
>       }
>    else
>       {
>       if ( v_dy >= 0 )
>          {
>          if ( half )
>             ang += 3072;
>          else
>             ang = 4096 - ang;
>          }
>       else
>          {
>          if ( half )
>             ang = 3072 - ang;
>          else
>             ang += 2048;
>          }
>       }
>
>    return ang;
>    }
>
>
>
>
>
>
>
>