org.locationtech.jts.triangulate.IncrementalDelaunayTriangulator Maven / Gradle / Ivy
/*
* Copyright (c) 2016 Vivid Solutions.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
*
* http://www.eclipse.org/org/documents/edl-v10.php.
*/
package org.locationtech.jts.triangulate;
import java.util.Collection;
import java.util.Iterator;
import org.locationtech.jts.triangulate.quadedge.LocateFailureException;
import org.locationtech.jts.triangulate.quadedge.QuadEdge;
import org.locationtech.jts.triangulate.quadedge.QuadEdgeSubdivision;
import org.locationtech.jts.triangulate.quadedge.Vertex;
/**
* Computes a Delaunay Triangulation of a set of {@link Vertex}es, using an
* incremental 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 MUST 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.
*
*
* @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.isInCircle(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);
}
}