/*
* The JTS Topology Suite is a collection of Java classes that
* implement the fundamental operations required to validate a given
* geo-spatial data set to a known topological specification.
*
* Copyright (C) 2001 Vivid Solutions
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* For more information, contact:
*
* Vivid Solutions
* Suite #1A
* 2328 Government Street
* Victoria BC V8T 5G5
* Canada
*
* (250)385-6040
* www.vividsolutions.com
*/
package com.vividsolutions.jts.triangulate;
import java.util.Collection;
import java.util.Iterator;
import com.vividsolutions.jts.triangulate.quadedge.LocateFailureException;
import com.vividsolutions.jts.triangulate.quadedge.QuadEdge;
import com.vividsolutions.jts.triangulate.quadedge.QuadEdgeSubdivision;
import com.vividsolutions.jts.triangulate.quadedge.Vertex;
/**
* Computes a Delauanay Triangulation of a set of {@link Vertex}es, using an
* incrementatal insertion algorithm.
*
* @author Martin Davis
* @version 1.0
*/
public class IncrementalDelaunayTriangulator
{
private QuadEdgeSubdivision subdiv;
private boolean isUsingTolerance = false;
/**
* Creates a new triangulator using the given {@link QuadEdgeSubdivision}.
* The triangulator uses the tolerance of the supplied subdivision.
*
* @param subdiv
* a subdivision in which to build the TIN
*/
public IncrementalDelaunayTriangulator(QuadEdgeSubdivision subdiv) {
this.subdiv = subdiv;
isUsingTolerance = subdiv.getTolerance() > 0.0;
}
/**
* Inserts all sites in a collection. The inserted vertices <b>MUST</b> be
* unique up to the provided tolerance value. (i.e. no two vertices should be
* closer than the provided tolerance value). They do not have to be rounded
* to the tolerance grid, however.
*
* @param vertices a Collection of Vertex
*
* @throws LocateFailureException if the location algorithm fails to converge in a reasonable number of iterations
*/
public void insertSites(Collection vertices) {
for (Iterator i = vertices.iterator(); i.hasNext();) {
Vertex v = (Vertex) i.next();
insertSite(v);
}
}
/**
* Inserts a new point into a subdivision representing a Delaunay
* triangulation, and fixes the affected edges so that the result is still a
* Delaunay triangulation.
* <p>
*
* @return a quadedge containing the inserted vertex
*/
public QuadEdge insertSite(Vertex v) {
/**
* This code is based on Guibas and Stolfi (1985), with minor modifications
* and a bug fix from Dani Lischinski (Graphic Gems 1993). (The modification
* I believe is the test for the inserted site falling exactly on an
* existing edge. Without this test zero-width triangles have been observed
* to be created)
*/
QuadEdge e = subdiv.locate(v);
if (subdiv.isVertexOfEdge(e, v)) {
// point is already in subdivision.
return e;
}
else if (subdiv.isOnEdge(e, v.getCoordinate())) {
// the point lies exactly on an edge, so delete the edge
// (it will be replaced by a pair of edges which have the point as a vertex)
e = e.oPrev();
subdiv.delete(e.oNext());
}
/**
* Connect the new point to the vertices of the containing triangle
* (or quadrilateral, if the new point fell on an existing edge.)
*/
QuadEdge base = subdiv.makeEdge(e.orig(), v);
QuadEdge.splice(base, e);
QuadEdge startEdge = base;
do {
base = subdiv.connect(e, base.sym());
e = base.oPrev();
} while (e.lNext() != startEdge);
// Examine suspect edges to ensure that the Delaunay condition
// is satisfied.
do {
QuadEdge t = e.oPrev();
if (t.dest().rightOf(e) && v.inCircle(e.orig(), t.dest(), e.dest())) {
QuadEdge.swap(e);
e = e.oPrev();
} else if (e.oNext() == startEdge) {
return base; // no more suspect edges.
} else {
e = e.oNext().lPrev();
}
} while (true);
}
}