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The OpenTripPlanner multimodal journey planning system
package org.opentripplanner.common.geometry;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Queue;
import java.util.Set;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.locationtech.jts.algorithm.CGAlgorithms;
import org.locationtech.jts.geom.Coordinate;
import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.GeometryFactory;
import org.locationtech.jts.geom.LinearRing;
import org.locationtech.jts.geom.Polygon;
/**
* Compute isoline based on a zFunc and a set of initial coverage points P0={(x,y)} to seed the
* computation.
*
* This assume we have a z = Fz(x,y) function which can gives a z value for any given point (x,y), z
* can be undefined for some region.
*
* There are many tricks to reduce to the minimum the numbers of Fz samplings, explained in the code
* below.
*
* It will compute an isoline for a given z0 value. The isoline is composed of a list of n polygons,
* CW for normal polygons, CCW for "holes". The isoline computation can be called multiple times on
* the same builder for different z0 values: this will reduce the number of Fz sampling as they are
* cached in the builder. Please note that the initial covering points must touch all isolines you
* want to cover.
*
* @author laurent
*/
public class RecursiveGridIsolineBuilder {
public interface ZFunc {
public long z(Coordinate c);
}
public enum Direction {
UP, DOWN, LEFT, RIGHT;
}
/**
* A fast XY-index for tiles, allowing to use maps.
*/
private static class XYIndex {
private int xIndex;
private int yIndex;
private XYIndex(int xIndex, int yIndex) {
this.xIndex = xIndex;
this.yIndex = yIndex;
}
private final XYIndex translated(int dx, int dy) {
return new XYIndex(this.xIndex + dx, this.yIndex + dy);
}
@Override
public final int hashCode() {
return xIndex >> 16 | yIndex;
}
@Override
public final boolean equals(Object other) {
if (other instanceof XYIndex) {
XYIndex otherTileIndex = (XYIndex) other;
return otherTileIndex.xIndex == this.xIndex && otherTileIndex.yIndex == this.yIndex;
}
return false;
}
@Override
public final String toString() {
return "(" + xIndex + "," + yIndex + ")";
}
}
private static class GridDot {
private XYIndex index;
private long z;
private GridEdge up, down, left, right;
private GridDot(XYIndex index, long z) {
this.index = index;
this.z = z;
}
@Override
public final int hashCode() {
return index.hashCode();
}
@Override
public final boolean equals(Object other) {
if (other instanceof GridDot) {
// Only compare position, not Z value which should be identical
return this.index.equals(((GridDot) other).index);
}
return false;
}
@Override
public final String toString() {
return "[Dot" + index + "," + z + "]";
}
}
private static class GridEdge {
// For horizontal edges, A is left and B is right
// For vertical edges, A is bottom and B is top
private GridDot A, B;
boolean horizontal;
int size;
boolean used = false;
private GridEdge(GridDot A, GridDot B, int size, boolean horizontal) {
// We accept A and B in any order. They must be correctly placed however
if (horizontal && A.index.xIndex > B.index.xIndex || !horizontal
&& A.index.yIndex > B.index.yIndex) {
// Must swap A and B
this.A = B;
this.B = A;
} else {
this.A = A;
this.B = B;
}
this.size = size;
this.horizontal = horizontal;
if (horizontal) {
if (this.A.index.yIndex != this.B.index.yIndex)
throw new AssertionError(
"Building horizontal edge with non horizontally-aligned dots");
if (this.B.index.xIndex - this.A.index.xIndex != size)
throw new AssertionError(
"Building horizontal edge with incorrect size vs dot spacing");
} else {
if (this.A.index.xIndex != this.B.index.xIndex)
throw new AssertionError(
"Building vertical edge with non vertically-aligned dots");
if (this.B.index.yIndex - this.A.index.yIndex != size)
throw new AssertionError(
"Building vertical edge with incorrect size vs dot spacing");
}
}
private final void indexEndPoints() {
if (size != 1)
throw new AssertionError("Can't dot-index edge with size != 1");
if (horizontal) {
A.right = this;
B.left = this;
} else {
A.up = this;
B.down = this;
}
}
private final int cut(long z0) {
if (A.z < z0 && z0 <= B.z)
return 1;
if (B.z < z0 && z0 <= A.z)
return -1;
return 0;
}
@Override
public final int hashCode() {
// Normally size does not matter as we won't
// keep edges from different sizes in the same set/map
// horizontality matter, though.
return A.hashCode() + size + (horizontal ? 0x8000 : 0);
}
@Override
public final boolean equals(Object other) {
if (other instanceof GridEdge) {
// Only compare A position, size and horizontality
GridEdge otherEdge = (GridEdge) other;
return A.equals(otherEdge.A) && size == otherEdge.size
&& horizontal == otherEdge.horizontal;
}
return false;
}
@Override
public final String toString() {
return "[" + (horizontal ? "H" : "V") + "-Edge" + A + "-" + B + " L=" + size + "]";
}
}
private static final Logger LOG = LoggerFactory.getLogger(RecursiveGridIsolineBuilder.class);
/**
* Size (in index-unit) of initial (seed) sampling. This *MUST* be a power of 2. Good values are
* 4 (slower but miss less small islands) or 8 (faster but miss more small islands).
*/
private static final int SIZE_0 = 4;
private ZFunc fz;
private int fzInterpolateCount;
private double dX, dY;
private Coordinate center;
private Map allDots;
private Set initialDots;
private List initialEdges;
private boolean debugSeedGrid = false;
private boolean debugCrossingEdges = false;
private Geometry debugGeometry = null;
// private List p0List;
/**
* Create an object to compute isochrones. One may call several time isochronify on the same
* IsoChronificator object, this will re-use the z = f(x,y) sampling if possible, as they are
* kept in cache.
*
* @param center Center point (eg origin)
* @param fz Function returning the z-value for a xy-coordinate
* @param p0List Initial set of coverage points to seed the heuristics
*/
public RecursiveGridIsolineBuilder( double dX, double dY, Coordinate center, ZFunc fz,
List p0List) {
this.dX = dX;
this.dY = dY;
/*
* Center position only purpose is to serve as a reference value to the XY integer indexing,
* so it only needs to be not too far off to prevent int indexes from overflowing.
*/
this.center = center;
// this.p0List = p0List;
LOG.debug("Center={} dX={} dY={}", this.center, dX, dY);
this.fz = fz;
/* Step 1. SEED (1). Compute initial set of dots. */
allDots = new HashMap(p0List.size() / 2);
initialDots = new HashSet(p0List.size() / 2);
for (Coordinate p0 : p0List) {
XYIndex index0 = getIndex(p0, SIZE_0);
for (int dx = -SIZE_0; dx <= SIZE_0; dx += SIZE_0) {
for (int dy = -SIZE_0; dy <= SIZE_0; dy += SIZE_0) {
// This will always create initial dots
GridDot A = getOrCreateDot(index0.translated(dx, dy));
initialDots.add(A);
}
}
}
/*
* Step 2. SEED (2). Create initial edges from initial dots. There will be slightly less
* edges than dots.
*/
initialEdges = new ArrayList(initialDots.size());
for (GridDot A : initialDots) {
// Horizontal
GridDot B = allDots.get(A.index.translated(SIZE_0, 0));
if (B != null) {
GridEdge e = new GridEdge(A, B, SIZE_0, true);
initialEdges.add(e);
}
// Vertical
B = allDots.get(A.index.translated(0, SIZE_0));
if (B != null) {
GridEdge e = new GridEdge(A, B, SIZE_0, false);
initialEdges.add(e);
}
}
LOG.debug("Created {} dots and {} edges out of {} initial points.", initialDots.size(),
initialEdges.size(), p0List.size());
}
public void setDebugSeedGrid(boolean debugSeedGrid) {
this.debugSeedGrid = debugSeedGrid;
}
public void setDebugCrossingEdges(boolean debugCrossingEdges) {
this.debugCrossingEdges = debugCrossingEdges;
}
public Geometry computeIsoline(long z0) {
fzInterpolateCount = 0;
GeometryFactory geomFactory = new GeometryFactory();
/*
* Step 3. DIVIDE. While there are cutting edges from size > 1 to divide, divide them in
* two. Note: edgesToExpand only contains cutting edges.
*/
Queue edgesToDivide = new ArrayDeque();
edgesToDivide.addAll(initialEdges);
Queue edgesToExpand = new ArrayDeque();
while (!edgesToDivide.isEmpty()) {
GridEdge e = edgesToDivide.remove();
if (e.cut(z0) == 0)
continue;
int size2 = e.size / 2;
XYIndex iC = e.horizontal ? e.A.index.translated(size2, 0) : e.A.index.translated(0,
size2);
GridDot C = getOrCreateDot(iC);
GridEdge e1 = new GridEdge(e.A, C, size2, e.horizontal);
GridEdge e2 = new GridEdge(C, e.B, size2, e.horizontal);
GridEdge eCut = e1.cut(z0) != 0 ? e1 : e2;
if (eCut.cut(z0) == 0)
throw new AssertionError("Edge MUST cut!");
if (size2 == 1) {
edgesToExpand.add(eCut);
} else {
edgesToDivide.add(eCut);
}
}
/*
* Step 4. EXPAND. While there are unprocessed cutting edges, expand them by looking around
* them for cutting edges.
*/
Set finalEdges = new HashSet();
Set finalNonCuttingEdges = new HashSet();
while (!edgesToExpand.isEmpty()) {
GridEdge e = edgesToExpand.remove();
if (finalEdges.add(e) == false) {
// Since we may have duplicates in the toExpand Q,
// we prune-out early processed elements.
continue;
}
/**
* Build the 6 remaining edges (e1..e6) around the 2 squares ABDC and DBFE touching e
*
*
* [Horizontal e] [Vertical e]
*
* C--(e2)--D D--(e3)--B--(e6)--F
* | | | | |
* (e1) (e3) (e2) (e) (e5)
* | | | | |
* A--(e)---B C--(e1)--A--(e4)--E
* | |
* (e4) (e6)
* | |
* E--(e5)--F
*
*/
XYIndex iC = e.horizontal ? e.A.index.translated(0, 1) : e.A.index.translated(-1, 0);
XYIndex iD = e.horizontal ? e.B.index.translated(0, 1) : e.B.index.translated(-1, 0);
XYIndex iE = e.horizontal ? e.A.index.translated(0, -1) : e.A.index.translated(1, 0);
XYIndex iF = e.horizontal ? e.B.index.translated(0, -1) : e.B.index.translated(1, 0);
GridDot C = getOrCreateDot(iC);
GridDot D = getOrCreateDot(iD);
GridDot E = getOrCreateDot(iE);
GridDot F = getOrCreateDot(iF);
GridEdge[] e2List = new GridEdge[] { new GridEdge(e.A, C, 1, !e.horizontal),
new GridEdge(C, D, 1, e.horizontal), new GridEdge(e.B, D, 1, !e.horizontal),
new GridEdge(e.A, E, 1, !e.horizontal), new GridEdge(E, F, 1, e.horizontal),
new GridEdge(e.B, F, 1, !e.horizontal) };
for (GridEdge e2 : e2List) {
if (e2.cut(z0) == 0) {
finalNonCuttingEdges.add(e2);
continue; // Do not cut, OK
}
if (finalEdges.contains(e2))
continue; // Already processed
edgesToExpand.add(e2);
}
}
/*
* Note: Here finalEdges only contains cutting edges, and should end up containing all
* cutting edges that are discoverable.
*/
for (GridEdge e : finalEdges) {
e.indexEndPoints();
}
for (GridEdge e : finalNonCuttingEdges) {
e.indexEndPoints();
}
// For later logs.
int finalEdgesSize = finalEdges.size();
int finalNonCuttingEdgesSize = finalNonCuttingEdges.size();
/*
* Step 5. BUILD. Build polygons from finalEdges set.
*/
List debugGeom = new ArrayList();
if (debugSeedGrid) {
for (GridEdge e : initialEdges) {
Coordinate A = getCoordinate(e.A.index);
Coordinate B = getCoordinate(e.B.index);
debugGeom.add(geomFactory.createLineString(new Coordinate[] { A, B }));
}
// for (Coordinate p0 : p0List) {
// debugGeom.add(geomFactory.createPoint(p0));
// }
}
if (debugCrossingEdges) {
for (GridEdge e : finalEdges) {
Coordinate A = getCoordinate(e.A.index);
Coordinate B = getCoordinate(e.B.index);
Coordinate C = interpolate(A, B, e.A.z, e.B.z, z0);
Coordinate C1 = new Coordinate(C.x + (B.y - A.y) * 0.1, C.y + (B.x - A.x) * 0.1);
Coordinate C2 = new Coordinate(C.x - (B.y - A.y) * 0.1, C.y - (B.x - A.x) * 0.1);
debugGeom
.add(geomFactory.createLineString(new Coordinate[] { A, C, C1, C2, C, B }));
}
}
List retval = new ArrayList();
List rings = new ArrayList();
while (!finalEdges.isEmpty()) {
GridEdge e0 = finalEdges.iterator().next();
List polyPoints = new ArrayList();
int cut = e0.cut(z0);
Direction direction = e0.horizontal ? (cut > 0 ? Direction.UP : Direction.DOWN)
: (cut > 0 ? Direction.LEFT : Direction.RIGHT);
GridEdge e = e0;
while (true) {
// Add a point to polyline
Coordinate cA = getCoordinate(e.A.index);
Coordinate cB = getCoordinate(e.B.index);
Coordinate cC = interpolate(cA, cB, e.A.z, e.B.z, z0);
polyPoints.add(cC);
e.used = true;
finalEdges.remove(e);
// Compute next edge from adjacent tile
// Here e1 is always on e.A side, e2 on e.B side
// and e3 on opposite side of tile from e.
GridEdge e1, e2, e3;
Direction d1, d2; // d3: same direction.
switch (direction) {
default: // Never happen
case UP:
e1 = e.A.up;
d1 = Direction.LEFT;
e2 = e.B.up;
d2 = Direction.RIGHT;
e3 = e1.B.right;
break;
case DOWN:
e1 = e.A.down;
d1 = Direction.LEFT;
e2 = e.B.down;
d2 = Direction.RIGHT;
e3 = e1.A.right;
break;
case LEFT:
e1 = e.A.left;
d1 = Direction.DOWN;
e2 = e.B.left;
d2 = Direction.UP;
e3 = e1.A.up;
break;
case RIGHT:
e1 = e.A.right;
d1 = Direction.DOWN;
e2 = e.B.right;
d2 = Direction.UP;
e3 = e1.B.up;
break;
}
boolean ok1 = e1.cut(z0) != 0 && !e1.used;
boolean ok2 = e2.cut(z0) != 0 && !e2.used;
boolean ok3 = e3.cut(z0) != 0 && !e3.used;
if (ok1 && ok2) {
/*
* We can go either turn, pick the best one from e1 or e2 by looking if C lies
* closer to e.A or e.B. Please note this is approximate only, as we should take
* into account real interpolated position on e1 and e2 to compute segment
* lenght. But this gives good approximated results and is probably sufficient
* given the approximated solution anyway.
*/
double dA = Math.max(Math.abs(cA.x - cC.x), Math.abs(cA.y - cC.y));
double dB = Math.max(Math.abs(cB.x - cC.x), Math.abs(cB.y - cC.y));
if (dA <= dB) {
// C closer to A
e = e1;
direction = d1;
} else {
// C closer to B
e = e2;
direction = d2;
}
} else if (ok1) {
e = e1;
direction = d1;
} else if (ok2) {
e = e2;
direction = d2;
} else if (ok3) {
e = e3;
// Same direction as before
} else {
// This must be the end of the polyline...
break;
}
}
// Close the polyline
polyPoints.add(polyPoints.get(0));
LinearRing ring = geomFactory.createLinearRing(polyPoints
.toArray(new Coordinate[polyPoints.size()]));
rings.add(ring);
}
retval.addAll(punchHoles(geomFactory, rings));
LOG.info("Isochrones: {}+{} Fz samples, {} cutting edges, {} non-cutting edges",
allDots.size(), fzInterpolateCount, finalEdgesSize, finalNonCuttingEdgesSize);
/*
* Step 6. CLEAN. Remove edge index from dots.
*/
for (GridDot A : allDots.values()) {
A.up = A.down = A.right = A.left = null;
}
debugGeometry = geomFactory.createGeometryCollection(debugGeom
.toArray(new Geometry[debugGeom.size()]));
return geomFactory.createGeometryCollection(retval.toArray(new Geometry[retval.size()]));
}
public final Geometry getDebugGeometry() {
return debugGeometry;
}
private final XYIndex getIndex(Coordinate p, int size) {
int xIndex = (int) Math.round((p.x - center.x) / dX);
int yIndex = (int) Math.round((p.y - center.y) / dY);
if (size != 1) {
int size2 = size / 2;
xIndex = (xIndex + (xIndex > 0 ? size2 : -size2)) / size * size;
yIndex = (yIndex + (yIndex > 0 ? size2 : -size2)) / size * size;
}
return new XYIndex(xIndex, yIndex);
}
private final Coordinate getCoordinate(XYIndex index) {
return new Coordinate(index.xIndex * dX + center.x, index.yIndex * dY + center.y);
}
private GridDot getOrCreateDot(XYIndex xyIndex) {
GridDot A = allDots.get(xyIndex);
if (A == null) {
A = new GridDot(xyIndex, fz.z(getCoordinate(xyIndex)));
allDots.put(xyIndex, A);
}
return A;
}
private final Coordinate interpolate(Coordinate A, Coordinate B, long zA, long zB, long z0) {
int n = 0;
while (n < 3 && (zA == Long.MAX_VALUE || zB == Long.MAX_VALUE)) {
Coordinate C = new Coordinate((A.x + B.x) / 2.0, (A.y + B.y) / 2.0);
long zC = fz.z(A);
fzInterpolateCount++;
if (zA == Long.MAX_VALUE && z0 <= zC) {
A = C;
zA = zC;
} else {
B = C;
zB = zC;
}
n++;
}
// Take as fallback position if we are still at +inf at one end z0 * 2
if (zA == Long.MAX_VALUE)
zA = z0 * 2;
if (zB == Long.MAX_VALUE)
zB = z0 * 2;
double k = zB == zA ? 0.5 : (z0 - zA) / (double) (zB - zA);
Coordinate C = new Coordinate(A.x * (1.0 - k) + B.x * k, A.y * (1.0 - k) + B.y * k);
return C;
}
@SuppressWarnings("unchecked")
private final List punchHoles(GeometryFactory geomFactory, List rings) {
List shells = new ArrayList(rings.size());
List holes = new ArrayList(rings.size() / 2);
// 1. Split the polygon list in two: shells and holes (CCW and CW)
for (LinearRing ring : rings) {
if (CGAlgorithms.signedArea(ring.getCoordinateSequence()) > 0.0)
holes.add(ring);
else
shells.add(geomFactory.createPolygon(ring));
}
// 2. Sort the shells based on number of points to optimize step 3.
Collections.sort(shells, new Comparator() {
@Override
public int compare(Polygon o1, Polygon o2) {
return o2.getNumPoints() - o1.getNumPoints();
}
});
for (Polygon shell : shells) {
shell.setUserData(new ArrayList());
}
// 3. For each hole, determine which shell it fits in.
for (LinearRing hole : holes) {
outer: {
// Probably most of the time, the first shell will be the one
for (Polygon shell : shells) {
if (shell.contains(hole)) {
((List) shell.getUserData()).add(hole);
break outer;
}
}
// This should not happen, but do not break bad here
// as loosing a hole is not critical, we still have
// sensible data to return.
LOG.error("Cannot find fitting shell for a hole!");
}
}
// 4. Build the list of punched polygons
List punched = new ArrayList(shells.size());
for (Polygon shell : shells) {
List shellHoles = ((List) shell.getUserData());
punched.add(geomFactory.createPolygon((LinearRing) (shell.getExteriorRing()),
shellHoles.toArray(new LinearRing[shellHoles.size()])));
}
return punched;
}
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