/* * Poly2Tri Copyright (c) 2009-2018, Poly2Tri Contributors * https://github.com/jhasse/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 */ #pragma once #include 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); /** * Requirement:
* 1. a,b and c form a triangle.
* 2. a and d is know to be on opposite side of bc
* 
   *                a
   *                +
   *               / \
   *              /   \
   *            b/     \c
   *            +-------+
   *           /    d    \
   *          /           \
   *
* Fact: d has to be in area B to have a chance to be inside the circle formed by * a,b and c
* d is outside B if orient2d(a,b,d) or orient2d(c,a,d) is CW
* 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(const Point& pa, const Point& pb, const Point& pc, const Point& pd) const; /** * Rotates a triangle pair one vertex CW *
   *       n2                    n2
   *  P +-----+             P +-----+
   *    | t  /|               |\  t |
   *    |   / |               | \   |
   *  n1|  /  |n3           n1|  \  |n3
   *    | /   |    after CW   |   \ |
   *    |/ oT |               | oT \|
   *    +-----+ oP            +-----+
   *       n4                    n4
   *
*/ void RotateTrianglePair(Triangle& t, Point& p, Triangle& ot, Point& op) const; /** * 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(const Node* node) const; bool AngleIsNegative(const Point* origin, const Point* pa, const Point* pb) const; bool AngleExceeds90Degrees(const Point* origin, const Point* pa, const Point* pb) const; bool AngleExceedsPlus90DegreesOrIsNegative(const Point* origin, const Point* pa, const Point* pb) const; double Angle(const Point* origin, const Point* pa, const Point* pb) const; /** * * @param node - middle node * @return the angle between 3 front nodes */ double HoleAngle(const Node& node) const; /** * The basin angle is decided against the horizontal line [1,0] */ double BasinAngle(const Node& node) const; /** * Fills a basin that has formed on the Advancing Front to the right * of given node.
* 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
* 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 nodes_; }; }