55 lines
1.4 KiB
C++
55 lines
1.4 KiB
C++
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#include <math.h> /* acos(), M_PI */
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#include "Polygon.h"
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#define FP_EQUAL(x,y) (fabs((x)-(y)) < 1E-6)
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/*
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* from http://local.wasp.uwa.edu.au/~pbourke/geometry/insidepoly/
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* Return the angle between two vectors on a plane
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* The angle is from vector 1 to vector 2, positive anticlockwise
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* The result is between -pi -> pi
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*/
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double angle2D(double x1, double y1, double x2, double y2)
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{
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double dtheta, theta1, theta2;
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theta1 = atan2(y1,x1);
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theta2 = atan2(y2,x2);
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dtheta = theta2 - theta1;
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while (dtheta > M_PI)
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dtheta -= 2.0 * M_PI;
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while (dtheta < -M_PI)
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dtheta += 2.0 * M_PI;
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return dtheta;
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}
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bool Polygon::containsPoint2D(const Vector & v) const
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{
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double angle_sum = 0.0;
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for (int i = 0, sz = size(); i < sz; i++)
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{
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Vector v1 = *(*this)[i] - v;
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Vector v2 = *(*this)[(i+1) % sz] - v;
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double angle = angle2D(v1[0], v1[1], v2[0], v2[1]);
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angle_sum += angle;
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}
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return FP_EQUAL(angle_sum, 2.0 * M_PI);
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}
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bool Polygon::containsPointConvex(const Vector & v) const
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{
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double angle_sum = 0.0;
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for (int i = 0, sz = size(); i < sz; i++)
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{
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Vector v1 = *(*this)[i] - v;
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Vector v2 = *(*this)[(i+1) % sz] - v;
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double cosine = (v1 % v2) / (v1.mag() * v2.mag());
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double angle = acos(cosine);
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angle_sum += angle;
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}
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return FP_EQUAL(angle_sum, 2.0 * M_PI);
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}
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