Subversion Repositories orsoc_graphics_accelerator

/*

 * 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,

 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR

 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF

 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING

 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

/**

 * 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 a - triangle point, opposite d

   * @param b - triangle point

   * @param c - triangle point

   * @param d - 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

   * @param cnt - counter used to alternate on even and odd numbers

   */

  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