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106 lines
3.2 KiB
C
106 lines
3.2 KiB
C
1 month ago
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/**********************************************************************
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*
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* GEOS - Geometry Engine Open Source
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* http://geos.osgeo.org
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*
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* Copyright (C) 2006 Refractions Research Inc.
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*
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* This is free software; you can redistribute and/or modify it under
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* the terms of the GNU Lesser General Public Licence as published
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* by the Free Software Foundation.
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* See the COPYING file for more information.
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*
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**********************************************************************/
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#ifndef GEOS_GEOM_TRIANGLE_H
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#define GEOS_GEOM_TRIANGLE_H
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#include <geos/export.h>
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#include <geos/geom/Coordinate.h>
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#include <geos/inline.h>
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namespace geos {
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namespace geom { // geos::geom
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/**
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* \brief
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* Represents a planar triangle, and provides methods for calculating various
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* properties of triangles.
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*/
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class GEOS_DLL Triangle {
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public:
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Coordinate p0, p1, p2;
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Triangle(const Coordinate& nP0, const Coordinate& nP1, const Coordinate& nP2)
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:
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p0(nP0),
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p1(nP1),
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p2(nP2)
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{}
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/** \brief
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* The inCentre of a triangle is the point which is equidistant
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* from the sides of the triangle.
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*
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* This is also the point at which the bisectors of the angles meet.
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*
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* @param resultPoint the point into which to write the inCentre of the triangle
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*/
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void inCentre(Coordinate& resultPoint);
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/** \brief
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* Computes the circumcentre of a triangle.
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*
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* The circumcentre is the centre of the circumcircle, the smallest circle
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* which encloses the triangle. It is also the common intersection point of
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* the perpendicular bisectors of the sides of the triangle, and is the only
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* point which has equal distance to all three vertices of the triangle.
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*
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* The circumcentre does not necessarily lie within the triangle. For example,
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* the circumcentre of an obtuse isoceles triangle lies outside the triangle.
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*
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* This method uses an algorithm due to J.R.Shewchuk which uses normalization
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* to the origin to improve the accuracy of computation. (See *Lecture Notes
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* on Geometric Robustness*, Jonathan Richard Shewchuk, 1999).
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*
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* @param resultPoint the point into which to write the inCentre of the triangle
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*/
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void circumcentre(Coordinate& resultPoint);
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void circumcentreDD(Coordinate& resultPoint);
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bool isIsoceles();
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/// Computes the circumcentre of a triangle.
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static const Coordinate circumcentre(const Coordinate& p0, const Coordinate& p1, const Coordinate& p2);
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private:
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/**
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* Computes the determinant of a 2x2 matrix. Uses standard double-precision
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* arithmetic, so is susceptible to round-off error.
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*
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* @param m00
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* the [0,0] entry of the matrix
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* @param m01
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* the [0,1] entry of the matrix
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* @param m10
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* the [1,0] entry of the matrix
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* @param m11
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* the [1,1] entry of the matrix
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* @return the determinant
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*/
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double det(double m00, double m01, double m10, double m11) const;
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};
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} // namespace geos::geom
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} // namespace geos
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//#ifdef GEOS_INLINE
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//# include "geos/geom/Triangle.inl"
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//#endif
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#endif // ndef GEOS_GEOM_TRIANGLE_H
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