path: root/polygon/poly2tri/sweep/sweep.h

/*
 * Poly2Tri Copyright (c) 2009-2010, Poly2Tri Contributors
 * http://code.google.com/p/poly2tri/
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * * Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 * * Neither the name of Poly2Tri nor the names of its contributors may be
 *   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
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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 */
/**
 * Sweep-line, Constrained Delauney Triangulation (CDT) See: Domiter, V. and
 * Zalik, B.(2008)'Sweep-line algorithm for constrained Delaunay triangulation',
 * International Journal of Geographical Information Science
 *
 * "FlipScan" Constrained Edge Algorithm invented by Thomas Åhlén, thahlen@gmail.com
 */

#ifndef SWEEP_H
#define SWEEP_H

#include <vector>

namespace p2t {

class SweepContext;
struct Node;
struct Point;
struct Edge;
class Triangle;

class Sweep
{
public:

  /**
   * Triangulate
   *
   * @param tcx
   */
  void Triangulate(SweepContext& tcx);

  /**
   * Destructor - clean up memory
   */
  ~Sweep();

private:

  /**
   * Start sweeping the Y-sorted point set from bottom to top
   *
   * @param tcx
   */
  void SweepPoints(SweepContext& tcx);

  /**
   * Find closes node to the left of the new point and
   * create a new triangle. If needed new holes and basins
   * will be filled to.
   *
   * @param tcx
   * @param point
   * @return
   */
  Node& PointEvent(SweepContext& tcx, Point& point);

   /**
     *
     *
     * @param tcx
     * @param edge
     * @param node
     */
  void EdgeEvent(SweepContext& tcx, Edge* edge, Node* node);

  void EdgeEvent(SweepContext& tcx, Point& ep, Point& eq, Triangle* triangle, Point& point);

  /**
   * Creates a new front triangle and legalize it
   *
   * @param tcx
   * @param point
   * @param node
   * @return
   */
  Node& NewFrontTriangle(SweepContext& tcx, Point& point, Node& node);

  /**
   * Adds a triangle to the advancing front to fill a hole.
   * @param tcx
   * @param node - middle node, that is the bottom of the hole
   */
  void Fill(SweepContext& tcx, Node& node);

  /**
   * Returns true if triangle was legalized
   */
  bool Legalize(SweepContext& tcx, Triangle& t);

  /**
   * <b>Requirement</b>:<br>
   * 1. a,b and c form a triangle.<br>
   * 2. a and d is know to be on opposite side of bc<br>
   * <pre>
   *                a
   *                +
   *               / \
   *              /   \
   *            b/     \c
   *            +-------+
   *           /    d    \
   *          /           \
   * </pre>
   * <b>Fact</b>: d has to be in area B to have a chance to be inside the circle formed by
   *  a,b and c<br>
   *  d is outside B if orient2d(a,b,d) or orient2d(c,a,d) is CW<br>
   *  This preknowledge gives us a way to optimize the incircle test
   * @param pa - triangle point, opposite d
   * @param pb - triangle point
   * @param pc - triangle point
   * @param pd - point opposite a
   * @return true if d is inside circle, false if on circle edge
   */
  bool Incircle(Point& pa, Point& pb, Point& pc, Point& pd);

  /**
   * Rotates a triangle pair one vertex CW
   *<pre>
   *       n2                    n2
   *  P +-----+             P +-----+
   *    | t  /|               |\  t |
   *    |   / |               | \   |
   *  n1|  /  |n3           n1|  \  |n3
   *    | /   |    after CW   |   \ |
   *    |/ oT |               | oT \|
   *    +-----+ oP            +-----+
   *       n4                    n4
   * </pre>
   */
  void RotateTrianglePair(Triangle& t, Point& p, Triangle& ot, Point& op);

  /**
   * Fills holes in the Advancing Front
   *
   *
   * @param tcx
   * @param n
   */
  void FillAdvancingFront(SweepContext& tcx, Node& n);

  // Decision-making about when to Fill hole.
  // Contributed by ToolmakerSteve2
  bool LargeHole_DontFill(Node* node);
  bool AngleExceeds90Degrees(Point* origin, Point* pa, Point* pb);
  bool AngleExceedsPlus90DegreesOrIsNegative(Point* origin, Point* pa, Point* pb);
  double Angle(Point& origin, Point& pa, Point& pb);

  /**
   *
   * @param node - middle node
   * @return the angle between 3 front nodes
   */
  double HoleAngle(Node& node);

  /**
   * The basin angle is decided against the horizontal line [1,0]
   */
  double BasinAngle(Node& node);

  /**
   * Fills a basin that has formed on the Advancing Front to the right
   * of given node.<br>
   * First we decide a left,bottom and right node that forms the
   * boundaries of the basin. Then we do a reqursive fill.
   *
   * @param tcx
   * @param node - starting node, this or next node will be left node
   */
  void FillBasin(SweepContext& tcx, Node& node);

  /**
   * Recursive algorithm to fill a Basin with triangles
   *
   * @param tcx
   * @param node - bottom_node
   */
  void FillBasinReq(SweepContext& tcx, Node* node);

  bool IsShallow(SweepContext& tcx, Node& node);

  bool IsEdgeSideOfTriangle(Triangle& triangle, Point& ep, Point& eq);

  void FillEdgeEvent(SweepContext& tcx, Edge* edge, Node* node);

  void FillRightAboveEdgeEvent(SweepContext& tcx, Edge* edge, Node* node);

  void FillRightBelowEdgeEvent(SweepContext& tcx, Edge* edge, Node& node);

  void FillRightConcaveEdgeEvent(SweepContext& tcx, Edge* edge, Node& node);

  void FillRightConvexEdgeEvent(SweepContext& tcx, Edge* edge, Node& node);

  void FillLeftAboveEdgeEvent(SweepContext& tcx, Edge* edge, Node* node);

  void FillLeftBelowEdgeEvent(SweepContext& tcx, Edge* edge, Node& node);

  void FillLeftConcaveEdgeEvent(SweepContext& tcx, Edge* edge, Node& node);

  void FillLeftConvexEdgeEvent(SweepContext& tcx, Edge* edge, Node& node);

  void FlipEdgeEvent(SweepContext& tcx, Point& ep, Point& eq, Triangle* t, Point& p);

  /**
   * After a flip we have two triangles and know that only one will still be
   * intersecting the edge. So decide which to contiune with and legalize the other
   *
   * @param tcx
   * @param o - should be the result of an orient2d( eq, op, ep )
   * @param t - triangle 1
   * @param ot - triangle 2
   * @param p - a point shared by both triangles
   * @param op - another point shared by both triangles
   * @return returns the triangle still intersecting the edge
   */
  Triangle& NextFlipTriangle(SweepContext& tcx, int o, Triangle&  t, Triangle& ot, Point& p, Point& op);

   /**
     * When we need to traverse from one triangle to the next we need
     * the point in current triangle that is the opposite point to the next
     * triangle.
     *
     * @param ep
     * @param eq
     * @param ot
     * @param op
     * @return
     */
  Point& NextFlipPoint(Point& ep, Point& eq, Triangle& ot, Point& op);

   /**
     * Scan part of the FlipScan algorithm<br>
     * When a triangle pair isn't flippable we will scan for the next
     * point that is inside the flip triangle scan area. When found
     * we generate a new flipEdgeEvent
     *
     * @param tcx
     * @param ep - last point on the edge we are traversing
     * @param eq - first point on the edge we are traversing
     * @param flipTriangle - the current triangle sharing the point eq with edge
     * @param t
     * @param p
     */
  void FlipScanEdgeEvent(SweepContext& tcx, Point& ep, Point& eq, Triangle& flip_triangle, Triangle& t, Point& p);

  void FinalizationPolygon(SweepContext& tcx);

  std::vector<Node*> nodes_;

};

}

#endif