#ifndef lint
static const char	RCSid[] = "$Id: fvect.c,v 2.6 2003/02/22 02:07:22 greg Exp $";
#endif
/*
 *  fvect.c - routines for floating-point vector calculations
 */

/* ====================================================================
 * The Radiance Software License, Version 1.0
 *
 * Copyright (c) 1990 - 2002 The Regents of the University of California,
 * through Lawrence Berkeley National Laboratory.   All rights reserved.
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 *           if any, must include the following acknowledgment:
 *             "This product includes Radiance software
 *                 (http://radsite.lbl.gov/)
 *                 developed by the Lawrence Berkeley National Laboratory
 *               (http://www.lbl.gov/)."
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 * 4. The names "Radiance," "Lawrence Berkeley National Laboratory"
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#include  <math.h>
#include  "fvect.h"


double
fdot(v1, v2)			/* return the dot product of two vectors */
register FVECT  v1, v2;
{
	return(DOT(v1,v2));
}


double
dist2(p1, p2)			/* return square of distance between points */
register FVECT  p1, p2;
{
	FVECT  delta;

	delta[0] = p2[0] - p1[0];
	delta[1] = p2[1] - p1[1];
	delta[2] = p2[2] - p1[2];

	return(DOT(delta, delta));
}


double
dist2line(p, ep1, ep2)		/* return square of distance to line */
FVECT  p;		/* the point */
FVECT  ep1, ep2;	/* points on the line */
{
	register double  d, d1, d2;

	d = dist2(ep1, ep2);
	d1 = dist2(ep1, p);
	d2 = d + d1 - dist2(ep2, p);

	return(d1 - 0.25*d2*d2/d);
}


double
dist2lseg(p, ep1, ep2)		/* return square of distance to line segment */
FVECT  p;		/* the point */
FVECT  ep1, ep2;	/* the end points */
{
	register double  d, d1, d2;

	d = dist2(ep1, ep2);
	d1 = dist2(ep1, p);
	d2 = dist2(ep2, p);

	if (d2 > d1) {			/* check if past endpoints */
		if (d2 - d1 > d)
			return(d1);
	} else {
		if (d1 - d2 > d)
			return(d2);
	}
	d2 = d + d1 - d2;

	return(d1 - 0.25*d2*d2/d);	/* distance to line */
}


void
fcross(vres, v1, v2)		/* vres = v1 X v2 */
register FVECT  vres, v1, v2;
{
	vres[0] = v1[1]*v2[2] - v1[2]*v2[1];
	vres[1] = v1[2]*v2[0] - v1[0]*v2[2];
	vres[2] = v1[0]*v2[1] - v1[1]*v2[0];
}


void
fvsum(vres, v0, v1, f)		/* vres = v0 + f*v1 */
register FVECT  vres, v0, v1;
register double  f;
{
	vres[0] = v0[0] + f*v1[0];
	vres[1] = v0[1] + f*v1[1];
	vres[2] = v0[2] + f*v1[2];
}


double
normalize(v)			/* normalize a vector, return old magnitude */
register FVECT  v;
{
	register double  len, d;
	
	d = DOT(v, v);
	
	if (d <= 0.0)
		return(0.0);
	
	if (d <= 1.0+FTINY && d >= 1.0-FTINY)
		len = 0.5 + 0.5*d;	/* first order approximation */
	else
		len = sqrt(d);

	v[0] *= d = 1.0/len;
	v[1] *= d;
	v[2] *= d;

	return(len);
}


void
spinvector(vres, vorig, vnorm, theta)	/* rotate vector around normal */
FVECT  vres, vorig, vnorm;
double  theta;
{
	double  sint, cost, normprod;
	FVECT  vperp;
	register int  i;
	
	if (theta == 0.0) {
		if (vres != vorig)
			VCOPY(vres, vorig);
		return;
	}
	cost = cos(theta);
	sint = sin(theta);
	normprod = DOT(vorig, vnorm)*(1.-cost);
	fcross(vperp, vnorm, vorig);
	for (i = 0; i < 3; i++)
		vres[i] = vorig[i]*cost + vnorm[i]*normprod + vperp[i]*sint;
}