com.vividsolutions.jts.noding.snapround.MCIndexSnapRounder Maven / Gradle / Ivy
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/*
* 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.noding.snapround;
import java.util.*;
import com.vividsolutions.jts.geom.*;
import com.vividsolutions.jts.algorithm.*;
import com.vividsolutions.jts.noding.*;
/**
* Uses Snap Rounding to compute a rounded,
* fully noded arrangement from a set of {@link SegmentString}s.
* Implements the Snap Rounding technique described in
* papers by Hobby, Guibas & Marimont, and Goodrich et al.
* Snap Rounding assumes that all vertices lie on a uniform grid;
* hence the precision model of the input must be fixed precision,
* and all the input vertices must be rounded to that precision.
*
* This implementation uses a monotone chains and a spatial index to
* speed up the intersection tests.
*
* This implementation appears to be fully robust using an integer precision model.
* It will function with non-integer precision models, but the
* results are not 100% guaranteed to be correctly noded.
*
* @version 1.7
*/
public class MCIndexSnapRounder
implements Noder
{
private final PrecisionModel pm;
private LineIntersector li;
private final double scaleFactor;
private MCIndexNoder noder;
private MCIndexPointSnapper pointSnapper;
private Collection nodedSegStrings;
public MCIndexSnapRounder(PrecisionModel pm) {
this.pm = pm;
li = new RobustLineIntersector();
li.setPrecisionModel(pm);
scaleFactor = pm.getScale();
}
public Collection getNodedSubstrings()
{
return NodedSegmentString.getNodedSubstrings(nodedSegStrings);
}
public void computeNodes(Collection inputSegmentStrings)
{
this.nodedSegStrings = inputSegmentStrings;
noder = new MCIndexNoder();
pointSnapper = new MCIndexPointSnapper(noder.getIndex());
snapRound(inputSegmentStrings, li);
// testing purposes only - remove in final version
//checkCorrectness(inputSegmentStrings);
}
private void checkCorrectness(Collection inputSegmentStrings)
{
Collection resultSegStrings = NodedSegmentString.getNodedSubstrings(inputSegmentStrings);
NodingValidator nv = new NodingValidator(resultSegStrings);
try {
nv.checkValid();
} catch (Exception ex) {
ex.printStackTrace();
}
}
private void snapRound(Collection segStrings, LineIntersector li)
{
List intersections = findInteriorIntersections(segStrings, li);
computeIntersectionSnaps(intersections);
computeVertexSnaps(segStrings);
}
/**
* Computes all interior intersections in the collection of {@link SegmentString}s,
* and returns their @link Coordinate}s.
*
* Does NOT node the segStrings.
*
* @return a list of Coordinates for the intersections
*/
private List findInteriorIntersections(Collection segStrings, LineIntersector li)
{
InteriorIntersectionFinderAdder intFinderAdder = new InteriorIntersectionFinderAdder(li);
noder.setSegmentIntersector(intFinderAdder);
noder.computeNodes(segStrings);
return intFinderAdder.getInteriorIntersections();
}
/**
* Snaps segments to nodes created by segment intersections.
*/
private void computeIntersectionSnaps(Collection snapPts)
{
for (Iterator it = snapPts.iterator(); it.hasNext(); ) {
Coordinate snapPt = (Coordinate) it.next();
HotPixel hotPixel = new HotPixel(snapPt, scaleFactor, li);
pointSnapper.snap(hotPixel);
}
}
/**
* Snaps segments to all vertices.
*
* @param edges the list of segment strings to snap together
*/
public void computeVertexSnaps(Collection edges)
{
for (Iterator i0 = edges.iterator(); i0.hasNext(); ) {
NodedSegmentString edge0 = (NodedSegmentString) i0.next();
computeVertexSnaps(edge0);
}
}
/**
* Snaps segments to the vertices of a Segment String.
*/
private void computeVertexSnaps(NodedSegmentString e)
{
Coordinate[] pts0 = e.getCoordinates();
for (int i = 0; i < pts0.length ; i++) {
HotPixel hotPixel = new HotPixel(pts0[i], scaleFactor, li);
boolean isNodeAdded = pointSnapper.snap(hotPixel, e, i);
// if a node is created for a vertex, that vertex must be noded too
if (isNodeAdded) {
e.addIntersection(pts0[i], i);
}
}
}
}