utils.h

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/*
 * Poly2Tri Copyright (c) 2009-2010, Poly2Tri Contributors
 * http://code.google.com/p/poly2tri/
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 * are permitted provided that the following conditions are met:
 *
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 *   this list of conditions and the following disclaimer.
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 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
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 *   used to endorse or promote products derived from this software without specific
 *   prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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 */
 
#ifndef UTILS_H
#define UTILS_H
 
#include <exception>
#include <cmath>
 
namespace p2t {
 
const double PI_3div4 = 3 * M_PI / 4;
const double PI_div2 = 1.57079632679489661923;
const double EPSILON = 1e-12;
 
enum Orientation { CW, CCW, COLLINEAR };

Orientation Orient2d(const Point& pa, const Point& pb, const Point& pc)
{
  double detleft = (pa.x - pc.x) * (pb.y - pc.y);
  double detright = (pa.y - pc.y) * (pb.x - pc.x);
  double val = detleft - detright;
  if (val > -EPSILON && val < EPSILON) {
    return COLLINEAR;
  } else if (val > 0) {
    return CCW;
  }
  return CW;
}
 
/*
bool InScanArea(Point& pa, Point& pb, Point& pc, Point& pd)
{
  double pdx = pd.x;
  double pdy = pd.y;
  double adx = pa.x - pdx;
  double ady = pa.y - pdy;
  double bdx = pb.x - pdx;
  double bdy = pb.y - pdy;
 
  double adxbdy = adx * bdy;
  double bdxady = bdx * ady;
  double oabd = adxbdy - bdxady;
 
  if (oabd <= EPSILON) {
    return false;
  }
 
  double cdx = pc.x - pdx;
  double cdy = pc.y - pdy;
 
  double cdxady = cdx * ady;
  double adxcdy = adx * cdy;
  double ocad = cdxady - adxcdy;
 
  if (ocad <= EPSILON) {
    return false;
  }
 
  return true;
}
 
*/
 
bool InScanArea(Point& pa, Point& pb, Point& pc, Point& pd)
{
  double oadb = (pa.x - pb.x)*(pd.y - pb.y) - (pd.x - pb.x)*(pa.y - pb.y);
  if (oadb >= -EPSILON) {
    return false;
  }
 
  double oadc = (pa.x - pc.x)*(pd.y - pc.y) - (pd.x - pc.x)*(pa.y - pc.y);
  if (oadc <= EPSILON) {
    return false;
  }
  return true;
}
 
}
 
#endif