/*
* 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.revolsys.geometry.noding.snapround;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import com.revolsys.geometry.algorithm.LineIntersector;
import com.revolsys.geometry.algorithm.RobustLineIntersector;
import com.revolsys.geometry.model.Point;
import com.revolsys.geometry.noding.InteriorIntersectionFinderAdder;
import com.revolsys.geometry.noding.MCIndexNoder;
import com.revolsys.geometry.noding.NodedSegmentString;
import com.revolsys.geometry.noding.Noder;
import com.revolsys.geometry.noding.SegmentString;
import com.revolsys.geometry.noding.SinglePassNoder;
/**
* Uses Snap Rounding to compute a rounded,
* fully noded arrangement from a set of {@link SegmentString}s.
* Implements the Snap Rounding technique described in
* the 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.
* <p>
* This implementation uses simple iteration over the line segments.
* This is not the most efficient approach for large sets of segments.
* <p>
* 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 SimpleSnapRounder implements Noder {
private final LineIntersector li;
private Collection nodedSegStrings;
private final double scaleFactor;
public SimpleSnapRounder(final double scale) {
this.scaleFactor = scale;
this.li = new RobustLineIntersector(this.scaleFactor);
}
/**
* @param inputSegmentStrings a Collection of NodedSegmentStrings
*/
@Override
public void computeNodes(final Collection<NodedSegmentString> inputSegmentStrings) {
this.nodedSegStrings = inputSegmentStrings;
snapRound(inputSegmentStrings, this.li);
// testing purposes only - remove in final version
// checkCorrectness(inputSegmentStrings);
}
/**
* Computes nodes introduced as a result of snapping segments to snap points (hot pixels)
* @param li
*/
private void computeSnaps(final Collection segStrings, final Collection snapPts) {
for (final Iterator i0 = segStrings.iterator(); i0.hasNext();) {
final NodedSegmentString ss = (NodedSegmentString)i0.next();
computeSnaps(ss, snapPts);
}
}
private void computeSnaps(final NodedSegmentString ss, final Collection<Point> snapPts) {
for (final Point snapPt : snapPts) {
final HotPixel hotPixel = new HotPixel(snapPt, this.scaleFactor, this.li);
for (int i = 0; i < ss.size() - 1; i++) {
hotPixel.addSnappedNode(ss, i);
}
}
}
/**
* Computes nodes introduced as a result of
* snapping segments to vertices of other segments
*
* @param edges the list of segment strings to snap together
*/
public void computeVertexSnaps(final Collection edges) {
for (final Iterator i0 = edges.iterator(); i0.hasNext();) {
final NodedSegmentString edge0 = (NodedSegmentString)i0.next();
for (final Iterator i1 = edges.iterator(); i1.hasNext();) {
final NodedSegmentString edge1 = (NodedSegmentString)i1.next();
computeVertexSnaps(edge0, edge1);
}
}
}
/**
* Performs a brute-force comparison of every segment in each {@link SegmentString}.
* This has n^2 performance.
*/
private void computeVertexSnaps(final NodedSegmentString segment1,
final NodedSegmentString segment2) {
for (int i0 = 0; i0 < segment1.size() - 1; i0++) {
final Point point1 = segment1.getPoint(i0);
final HotPixel hotPixel = new HotPixel(point1, this.scaleFactor, this.li);
for (int i1 = 0; i1 < segment2.size() - 1; i1++) {
// don't snap a vertex to itself
if (segment1 == segment2) {
if (i0 == i1) {
continue;
}
}
// System.out.println("trying " + pts0[i0] + " against " + pts1[i1] +
// pts1[i1 + 1]);
final boolean isNodeAdded = hotPixel.addSnappedNode(segment2, i1);
// if a node is created for a vertex, that vertex must be noded too
if (isNodeAdded) {
segment1.addIntersection(point1, i0);
}
}
}
}
/**
* Computes all interior intersections in the collection of {@link SegmentString}s,
* and returns their {@link Coordinates}s.
*
* Does NOT node the segStrings.
*
* @return a list of Point for the intersections
*/
private List findInteriorIntersections(final Collection segStrings, final LineIntersector li) {
final InteriorIntersectionFinderAdder intFinderAdder = new InteriorIntersectionFinderAdder(li);
final SinglePassNoder noder = new MCIndexNoder();
noder.setSegmentIntersector(intFinderAdder);
noder.computeNodes(segStrings);
return intFinderAdder.getInteriorIntersections();
}
/**
* @return a Collection of NodedSegmentStrings representing the substrings
*
*/
@Override
public Collection<NodedSegmentString> getNodedSubstrings() {
return NodedSegmentString.getNodedSubstrings(this.nodedSegStrings);
}
private void snapRound(final Collection segStrings, final LineIntersector li) {
final List intersections = findInteriorIntersections(segStrings, li);
computeSnaps(segStrings, intersections);
computeVertexSnaps(segStrings);
}
}