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geometry.h

/*
 * vim: ts=4 sw=4 et tw=0 wm=0
 *
 * libavoid - Fast, Incremental, Object-avoiding Line Router
 * Copyright (C) 2004-2006  Michael Wybrow <mjwybrow@users.sourceforge.net>
 *
 * --------------------------------------------------------------------
 * Much of the code in this module is based on code published with
 * and/or described in "Computational Geometry in C" (Second Edition),
 * Copyright (C) 1998  Joseph O'Rourke <orourke@cs.smith.edu>
 * --------------------------------------------------------------------
 * The segmentIntersectPoint function is based on code published and
 * described in Franklin Antonio, Faster Line Segment Intersection,
 * Graphics Gems III, p. 199-202, code: p. 500-501.
 * --------------------------------------------------------------------
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 * 
*/


#ifndef _GEOMETRY_H
#define _GEOMETRY_H

#include "libavoid/geomtypes.h"

namespace Avoid {


extern double dist(const Point& a, const Point& b);
extern double totalLength(const Polygn& poly);
extern double angle(const Point& a, const Point& b, const Point& c);
extern bool segmentIntersect(const Point& a, const Point& b,
        const Point& c, const Point& d);
extern bool inPoly(const Polygn& poly, const Point& q);
extern bool inPolyGen(const Polygn& poly, const Point& q);
extern bool inValidRegion(bool IgnoreRegions, const Point& a0,
        const Point& a1, const Point& a2, const Point& b);
extern int cornerSide(const Point &c1, const Point &c2, const Point &c3,
        const Point& p);


// Direction from vector.
// Looks at the position of point c from the directed segment ab and
// returns the following:
//      1   counterclockwise
//      0   collinear
//     -1   clockwise
//
// Based on the code of 'AreaSign'.
//
static inline int vecDir(const Point& a, const Point& b, const Point& c)
{
    double area2 = ((b.x - a.x) * (c.y - a.y)) -
                   ((c.x - a.x) * (b.y - a.y));
    
    if (area2 < -0.001)
    {
        return -1;
    }
    else if (area2 > 0.001)
    {
        return 1;
    }
    return 0;
}

// Finds the projection point of (a,b) onto (a,c)
static inline Point projection(const Point& a, const Point& b, const Point& c)
{
    double ux = c.x - a.x,
           uy = c.y - a.y,
           vx = b.x - a.x,
           vy = b.y - a.y,
           scalarProj = ux * vx + uy * vy;
    scalarProj       /= ux * ux + uy * uy;
    Point p;
    p.x = scalarProj * ux + a.x;
    p.y = scalarProj * uy + a.y;
    return p;
}

// Line Segment Intersection
// Original code by Franklin Antonio 
// 
static const int DONT_INTERSECT = 0;
static const int DO_INTERSECT = 1;
static const int PARALLEL = 3;
extern int segmentIntersectPoint(const Point& a1, const Point& a2,
        const Point& b1, const Point& b2, double *x, double *y);


}


#endif

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