Path: chuka.playstation.co.uk!news
From: "Craig Graham" <c_graham@hinge.mistral.co.uk>
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: Re: Rotation, ApplyMatrix Query (fairly long)
Date: 25 Mar 1998 09:15:46 GMT
Organization: PlayStation Net Yaroze (SCEE)
Lines: 44
Message-ID: <01bd57cf$3c521120$72d449c2@Angela1.intelligent-group.com>
References: <34F3EFA2.4CD2@127.0.0.1> <350F949B.93337AA2@immd9.informatik.uni-erlangen.de> <351131B3.FC7030EB@intelligent-group.com> <35125A99.CB324946@immd9.informatik.uni-erlangen.de> <35165600.B98FF682@intelligent-group.com>
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Been waffling about manhattan distance approximation (approximate length of
a 3D vector), here's the code for it:

short manhatan_distance(short a, short b, short c)
{
        register short t;
        
        a=ABS(a);
        b=ABS(b);
        c=ABS(c);
        
        if(a<b)                         // a is > b
        {
                t=a;
                a=b;
                b=t;
        }
                
        if(b<c)                         // b is > c
        {
                t=b;
                b=c;
                c=t;
        }

        if(a<b)                         // a is > b
        {
                t=a;
                a=b;
                b=t;
        }
        
#ifdef FAST_BUT_LESS_ACCURATE        
      t=a + (b>>2) + (c>>2);	// faster (shift only, no multiply)
#else
      t=a + ((11*b)>>5) + (c>>2);	// more accurate but has an extra
multiply
#endif
        
        return t;
}

Craig