/*
* 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
* 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 PrecisionModel pm;
private LineIntersector li;
private final double scaleFactor;
private Collection nodedSegStrings;
public SimpleSnapRounder(PrecisionModel pm) {
this.pm = pm;
li = new RobustLineIntersector();
li.setPrecisionModel(pm);
scaleFactor = pm.getScale();
}
/**
* @return a Collection of NodedSegmentStrings representing the substrings
*
*/
public Collection getNodedSubstrings()
{
return NodedSegmentString.getNodedSubstrings(nodedSegStrings);
}
/**
* @param inputSegmentStrings a Collection of NodedSegmentStrings
*/
public void computeNodes(Collection inputSegmentStrings)
{
this.nodedSegStrings = inputSegmentStrings;
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);
computeSnaps(segStrings, 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)
{
IntersectionFinderAdder intFinderAdder = new IntersectionFinderAdder(li);
SinglePassNoder noder = new MCIndexNoder();
noder.setSegmentIntersector(intFinderAdder);
noder.computeNodes(segStrings);
return intFinderAdder.getInteriorIntersections();
}
/**
* Computes nodes introduced as a result of snapping segments to snap points (hot pixels)
* @param li
*/
private void computeSnaps(Collection segStrings, Collection snapPts)
{
for (Iterator i0 = segStrings.iterator(); i0.hasNext(); ) {
NodedSegmentString ss = (NodedSegmentString) i0.next();
computeSnaps(ss, snapPts);
}
}
private void computeSnaps(NodedSegmentString ss, Collection snapPts)
{
for (Iterator it = snapPts.iterator(); it.hasNext(); ) {
Coordinate snapPt = (Coordinate) it.next();
HotPixel hotPixel = new HotPixel(snapPt, scaleFactor, 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(Collection edges)
{
for (Iterator i0 = edges.iterator(); i0.hasNext(); ) {
NodedSegmentString edge0 = (NodedSegmentString) i0.next();
for (Iterator i1 = edges.iterator(); i1.hasNext(); ) {
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(NodedSegmentString e0, NodedSegmentString e1)
{
Coordinate[] pts0 = e0.getCoordinates();
Coordinate[] pts1 = e1.getCoordinates();
for (int i0 = 0; i0 < pts0.length - 1; i0++) {
HotPixel hotPixel = new HotPixel(pts0[i0], scaleFactor, li);
for (int i1 = 0; i1 < pts1.length - 1; i1++) {
// don't snap a vertex to itself
if (e0 == e1) {
if (i0 == i1) continue;
}
//System.out.println("trying " + pts0[i0] + " against " + pts1[i1] + pts1[i1 + 1]);
boolean isNodeAdded = hotPixel.addSnappedNode(e1, i1);
// if a node is created for a vertex, that vertex must be noded too
if (isNodeAdded) {
e0.addIntersection(pts0[i0], i0);
}
}
}
}
}