PolygonEarClipper.h

/**********************************************************************
 *
 * GEOS - Geometry Engine Open Source
 * http://geos.osgeo.org
 *
 * Copyright (C) 2020 Paul Ramsey <pramsey@cleverelephant.ca>
 *
 * This is free software; you can redistribute and/or modify it under
 * the terms of the GNU Lesser General Public Licence as published
 * by the Free Software Foundation.
 * See the COPYING file for more information.
 *
 **********************************************************************/
 
#pragma once
 
#include <geos/index/VertexSequencePackedRtree.h>
#include <geos/triangulate/tri/TriList.h>
#include <geos/triangulate/tri/Tri.h>
#include <geos/constants.h>
 
#include <array>
#include <memory>
#include <limits>
 
// Forward declarations
namespace geos {
namespace geom {
class Coordinate;
class Polygon;
class Envelope;
}
}
 
namespace geos {
namespace triangulate {
namespace polygon {
 
 
class GEOS_DLL PolygonEarClipper {
    using Coordinate = geos::geom::Coordinate;
    using CoordinateSequence = geos::geom::CoordinateSequence;
    using Polygon = geos::geom::Polygon;
    using Envelope = geos::geom::Envelope;
    using Tri = geos::triangulate::tri::Tri;
    template<typename TriType>
    using TriList = geos::triangulate::tri::TriList<TriType>;
    using VertexSequencePackedRtree = geos::index::VertexSequencePackedRtree;
 
private:
 
    // Members
 
    bool isFlatCornersSkipped = false;
 
    const CoordinateSequence& vertex;
    std::vector<std::size_t> vertexNext;
    std::size_t vertexSize;
 
    // first available vertex index
    std::size_t vertexFirst;
 
    // indices for current corner
    std::array<std::size_t, 3> cornerIndex;
 
    VertexSequencePackedRtree vertexCoordIndex;
 
    // Methods
 
    std::vector<std::size_t> createNextLinks(std::size_t size) const;
 
    bool isValidEar(std::size_t cornerIndex, const std::array<Coordinate, 3>& corner);
 
    std::size_t findIntersectingVertex(std::size_t cornerIndex, const std::array<Coordinate, 3>& corner) const;
 
    bool isValidEarScan(std::size_t cornerIndex, const std::array<Coordinate, 3>& corner) const;
 
    /* private  */
    static Envelope envelope(const std::array<Coordinate, 3>& corner);
 
    void removeCorner();
 
    bool isRemoved(std::size_t vertexIndex) const;
 
    void initCornerIndex();
 
    void fetchCorner(std::array<Coordinate, 3>& cornerVertex) const;
 
    void nextCorner(std::array<Coordinate, 3>& cornerVertex);
 
    std::size_t nextIndex(std::size_t index) const;
 
    bool isConvex(const std::array<Coordinate, 3>& pts) const;
 
    bool isFlat(const std::array<Coordinate, 3>& pts) const;
 
    bool isCornerInvalid(const std::array<Coordinate, 3>& pts) const;
 
 
public:
 
    PolygonEarClipper(const geom::CoordinateSequence& polyShell);
 
    static void triangulate(const geom::CoordinateSequence& polyShell, TriList<Tri>& triListResult);
 
    void setSkipFlatCorners(bool p_isFlatCornersSkipped);
 
    void compute(TriList<Tri>& triList);
 
    std::unique_ptr<Polygon> toGeometry() const;
 
 
};
 
 
 
} // namespace geos.triangulate.polygon
} // namespace geos.triangulate
} // namespace geos