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#ifndef lint |
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static const char RCSid[] = "$Id: fvect.c,v 1.4 2003/02/28 20:11:29 greg Exp $"; |
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#endif |
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/* |
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* Routines for 3-d vectors |
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*/ |
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|
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#include <stdio.h> |
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#include <stdlib.h> |
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#include <math.h> |
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#include "parser.h" |
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|
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|
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double |
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normalize(v) /* normalize a vector, return old magnitude */ |
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register FVECT v; |
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{ |
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static double len; |
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|
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len = DOT(v, v); |
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|
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if (len <= 0.0) |
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return(0.0); |
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|
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if (len <= 1.0+FTINY && len >= 1.0-FTINY) |
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len = 0.5 + 0.5*len; /* first order approximation */ |
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else |
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len = sqrt(len); |
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|
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v[0] /= len; |
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v[1] /= len; |
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v[2] /= len; |
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|
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return(len); |
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} |
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|
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|
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void |
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fcross(vres, v1, v2) /* vres = v1 X v2 */ |
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register FVECT vres, v1, v2; |
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{ |
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vres[0] = v1[1]*v2[2] - v1[2]*v2[1]; |
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vres[1] = v1[2]*v2[0] - v1[0]*v2[2]; |
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vres[2] = v1[0]*v2[1] - v1[1]*v2[0]; |
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} |
