programming-examples/java/Data_Structures/DelaunayVoronoi.java

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2019-11-15 12:59:38 +01:00
import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;
import java.util.*;
import java.util.List;
import java.util.Queue;
public class DelaunayVoronoi extends JFrame {
static class SubDivision {
List<QuadEdge> quadEdges = new ArrayList<>();
QuadEdge startingEdge;
static final double tolerance = 0.001;
Point.Double[] frameVertex = new Point.Double[3];
private QuadEdge lastEdge = null;
SubDivision(Collection<Point.Double> siteCoords) {
double minX = Double.POSITIVE_INFINITY;
double maxX = Double.NEGATIVE_INFINITY;
double minY = Double.POSITIVE_INFINITY;
double maxY = Double.NEGATIVE_INFINITY;
for (Point.Double p : siteCoords) {
minX = Math.min(minX, p.x);
maxX = Math.max(maxX, p.x);
minY = Math.min(minX, p.y);
maxY = Math.max(maxX, p.y);
}
double offset = Math.max(maxX - minX, maxX - minX) * 10;
frameVertex[0] = new Point.Double((maxX + minX) / 2, maxY + offset);
frameVertex[1] = new Point.Double(minX - offset, minY - offset);
frameVertex[2] = new Point.Double(maxX + offset, minY - offset);
QuadEdge a = makeEdge(frameVertex[0], frameVertex[1]);
QuadEdge b = makeEdge(frameVertex[1], frameVertex[2]);
QuadEdge.splice(a.sym(), b);
QuadEdge c = makeEdge(frameVertex[2], frameVertex[0]);
QuadEdge.splice(b.sym(), c);
QuadEdge.splice(c.sym(), a);
startingEdge = a;
}
QuadEdge makeEdge(Point.Double o, Point.Double d) {
QuadEdge q = QuadEdge.makeEdge(o, d);
quadEdges.add(q);
return q;
}
QuadEdge connect(QuadEdge a, QuadEdge b) {
QuadEdge q = QuadEdge.connect(a, b);
quadEdges.add(q);
return q;
}
void delete(QuadEdge e) {
QuadEdge.splice(e, e.oPrev());
QuadEdge.splice(e.sym(), e.sym().oPrev());
QuadEdge eSym = e.sym();
QuadEdge eRot = e.rot();
QuadEdge eRotSym = e.rot().sym();
// this is inefficient on an ArrayList, but this method should be called infrequently
quadEdges.remove(e);
quadEdges.remove(eSym);
quadEdges.remove(eRot);
quadEdges.remove(eRotSym);
e.delete();
eSym.delete();
eRot.delete();
eRotSym.delete();
}
// The edge returned has the property that either v is on e, or e is an edge of a triangle containing v.
QuadEdge locate(Point.Double v) {
if (lastEdge == null || !lastEdge.isNotDeleted()) {
lastEdge = quadEdges.iterator().next();
}
QuadEdge e = lastEdge;
for (int iter = 0; ; iter++) {
if (iter > quadEdges.size()) {
throw new RuntimeException("Possible topology error");
}
if (v.equals(e.orig()) || v.equals(e.dest())) {
break;
} else if (rightOf(v, e)) {
e = e.sym();
} else if (!rightOf(v, e.oNext())) {
e = e.oNext();
} else if (!rightOf(v, e.dPrev())) {
e = e.dPrev();
} else {
// on edge or in triangle containing edge
// System.out.println("Locate count: " + iter);
break;
}
}
return e;
}
// Tests whether a QuadEdge is an edge incident on a frame triangle vertex
boolean isFrameEdge(QuadEdge e) {
return isFrameVertex(e.orig()) || isFrameVertex(e.dest());
}
boolean isFrameVertex(Point.Double v) {
return v.equals(frameVertex[0]) || v.equals(frameVertex[1]) || v.equals(frameVertex[2]);
}
static double distancePointLine(Point.Double p, Point.Double A, Point.Double B) {
if (A.x == B.x && A.y == B.y) return p.distance(A);
double r = ((p.x - A.x) * (B.x - A.x) + (p.y - A.y) * (B.y - A.y)) / ((B.x - A.x) * (B.x - A.x) + (B.y - A.y) * (B.y - A.y));
if (r <= 0.0) return p.distance(A);
if (r >= 1.0) return p.distance(B);
double s = ((A.y - p.y) * (B.x - A.x) - (A.x - p.x) * (B.y - A.y)) / ((B.x - A.x) * (B.x - A.x) + (B.y - A.y) * (B.y - A.y));
return Math.abs(s) * Math.sqrt(((B.x - A.x) * (B.x - A.x) + (B.y - A.y) * (B.y - A.y)));
}
static boolean isOnEdge(QuadEdge e, Point.Double p) {
double dist = distancePointLine(p, e.orig(), e.dest());
double EDGE_COINCIDENCE_TOL_FACTOR = 1000;
return dist < tolerance / EDGE_COINCIDENCE_TOL_FACTOR;
}
boolean isEndPointOfEdge(QuadEdge e, Point.Double v) {
return equals(v, e.orig(), tolerance) || equals(v, e.dest(), tolerance);
}
// A TriangleVisitor which computes and sets the circumCenter as the origin of the dual edges originating in each triangle
static class TriangleCircumcentreVisitor implements TriangleVisitor {
public void visit(QuadEdge[] triEdges) {
Point.Double cc = circumCenter(triEdges[0].orig(), triEdges[1].orig(), triEdges[2].orig());
// save the circumCenter as the origin for the dual edges originating in this triangle
triEdges[0].rot().setOrig(cc);
triEdges[1].rot().setOrig(cc);
triEdges[2].rot().setOrig(cc);
}
static Point.Double circumCenter(Point.Double a, Point.Double b, Point.Double c) {
double Bx = b.x - a.x;
double By = b.y - a.y;
double Cx = c.x - a.x;
double Cy = c.y - a.y;
double d = 2 * (Bx * Cy - By * Cx);
double z1 = Bx * Bx + By * By;
double z2 = Cx * Cx + Cy * Cy;
double cx = Cy * z1 - By * z2;
double cy = Bx * z2 - Cx * z1;
return new Point.Double(cx / d + a.x, cy / d + a.y);
}
}
// Stores the edges for a visited triangle. Also pushes sym (neighbour) edges on stack to visit later.
QuadEdge[] fetchTriangleToVisit(QuadEdge edge, Queue<QuadEdge> edgeStack, boolean includeFrame, Set<QuadEdge> visitedEdges) {
QuadEdge[] triEdges = new QuadEdge[3];
QuadEdge curr = edge;
int edgeCount = 0;
boolean isFrame = false;
do {
triEdges[edgeCount] = curr;
if (isFrameEdge(curr))
isFrame = true;
// push sym edges to visit next
QuadEdge sym = curr.sym();
if (!visitedEdges.contains(sym))
edgeStack.add(sym);
// mark this edge as visited
visitedEdges.add(curr);
edgeCount++;
curr = curr.lNext();
} while (curr != edge);
return isFrame && !includeFrame ? null : triEdges;
}
void visitTriangles(TriangleVisitor triVisitor, boolean includeFrame) {
Queue<QuadEdge> q = new ArrayDeque<>();
q.add(startingEdge);
Set<QuadEdge> visitedEdges = Collections.newSetFromMap(new IdentityHashMap<>());
while (!q.isEmpty()) {
QuadEdge edge = q.remove();
if (!visitedEdges.contains(edge)) {
QuadEdge[] triEdges = fetchTriangleToVisit(edge, q, includeFrame, visitedEdges);
if (triEdges != null)
triVisitor.visit(triEdges);
}
}
}
/**
* Gets a collection of {@link QuadEdge}s whose origin
* vertices are a unique set which includes
* all vertices in the subdivision.
* The frame vertices can be included if required.
* <p>
* This is useful for algorithms which require traversing the
* subdivision starting at all vertices.
* Returning a quadedge for each vertex
* is more efficient than
* the alternative of finding the actual vertices
* quadedges attached to them.
*
* @param includeFrame true if the frame vertices should be included
* @return a collection of QuadEdge with the vertices of the subdivision as their origins
*/
List<QuadEdge> getVertexUniqueEdges(boolean includeFrame) {
List<QuadEdge> edges = new ArrayList<>();
Set<Point.Double> visitedVertices = new HashSet<>();
for (QuadEdge qe : quadEdges) {
Point.Double v = qe.orig();
if (!visitedVertices.contains(v)) {
visitedVertices.add(v);
if (includeFrame || !isFrameVertex(v)) {
edges.add(qe);
}
}
/**
* Inspect the sym edge as well, since it is
* possible that a vertex is only at the
* dest of all tracked quadedges.
*/
QuadEdge qd = qe.sym();
Point.Double vd = qd.orig();
if (!visitedVertices.contains(vd)) {
visitedVertices.add(vd);
if (includeFrame || !isFrameVertex(vd)) {
edges.add(qd);
}
}
}
return edges;
}
// Gets the coordinates for each triangle in the subdivision as an array
List<Point.Double[]> getTriangleCoordinates() {
TriangleCoordinatesVisitor visitor = new TriangleCoordinatesVisitor();
visitTriangles(visitor, false);
return visitor.getTriangles();
}
static class TriangleCoordinatesVisitor implements TriangleVisitor {
private List<Point.Double[]> triCoords = new ArrayList<>();
public void visit(QuadEdge[] triEdges) {
Point.Double[] coords = new Point.Double[4];
for (int i = 0; i < 3; i++) {
coords[i] = triEdges[i].orig();
}
coords[3] = coords[0];
triCoords.add(coords);
}
List<Point.Double[]> getTriangles() {
return triCoords;
}
}
/**
* Gets a List of {@link Polygon}s for the Voronoi cells
* of this triangulation.
* <p>
* The userData of each polygon is set to be the {@link Point.Double)
* of the cell site. This allows easily associating external
* data associated with the sites to the cells.
*
* @param geomFact a geometry factory
* @return a List of Polygons
*/
List<Point.Double[]> getVoronoiCellPolygons() {
/*
* Compute circumcentres of triangles as vertices for dual edges.
* Precomputing the circumcentres is more efficient,
* and more importantly ensures that the computed centres
* are consistent across the Voronoi cells.
*/
visitTriangles(new TriangleCircumcentreVisitor(), true);
List<Point.Double[]> cells = new ArrayList<>();
for (QuadEdge qe : getVertexUniqueEdges(false)) {
cells.add(getVoronoiCellPolygon(qe));
}
return cells;
}
/**
* Gets the Voronoi cell around a site specified
* by the origin of a QuadEdge.
* <p>
* The userData of the polygon is set to be the {@link Point.Double)
* of the site. This allows attaching external
* data associated with the site to this cell polygon.
*
* @param qe a quadedge originating at the cell site
* @param geomFact a factory for building the polygon
* @return a polygon indicating the cell extent
*/
Point.Double[] getVoronoiCellPolygon(QuadEdge qe) {
List<Point.Double> coordList = new ArrayList<>();
QuadEdge startQE = qe;
do {
Point.Double cc = qe.rot().orig();
coordList.add(cc);
// move to next triangle CW around vertex
qe = qe.oPrev();
} while (qe != startQE);
coordList.add(coordList.get(0));
if (coordList.size() < 4) {
System.out.println(coordList);
coordList.add(coordList.get(coordList.size() - 1));
}
Point.Double v = startQE.orig();
Point.Double[] pts = coordList.toArray(new Point.Double[0]);
return pts;
}
interface TriangleVisitor {
void visit(QuadEdge[] triEdges);
}
/**
* 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
*/
QuadEdge insertSite(Point.Double 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 = locate(v);
if (isEndPointOfEdge(e, v)) {
// point is already in subdivision.
return e;
} else if (isOnEdge(e, v)) {
// 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();
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 = makeEdge(e.orig(), v);
QuadEdge.splice(base, e);
QuadEdge startEdge = base;
do {
base = 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 (rightOf(t.dest(), e) && isInCircle(e.orig(), t.dest(), e.dest(), v)) {
QuadEdge.swap(e);
e = e.oPrev();
} else if (e.oNext() == startEdge) {
return base; // no more suspect edges.
} else {
e = e.oNext().lPrev();
}
} while (true);
}
static boolean equals(Point.Double p1, Point.Double p2, double tolerance) {
return p1.distance(p2) < tolerance;
}
static boolean isInCircle(Point.Double a, Point.Double b, Point.Double c, Point.Double p) {
double adx = a.x - p.x;
double ady = a.y - p.y;
double bdx = b.x - p.x;
double bdy = b.y - p.y;
double cdx = c.x - p.x;
double cdy = c.y - p.y;
double abdet = adx * bdy - bdx * ady;
double bcdet = bdx * cdy - cdx * bdy;
double cadet = cdx * ady - adx * cdy;
double alift = adx * adx + ady * ady;
double blift = bdx * bdx + bdy * bdy;
double clift = cdx * cdx + cdy * cdy;
double disc = alift * bcdet + blift * cadet + clift * abdet;
return disc > 0;
}
static boolean isCCW(Point.Double a, Point.Double b, Point.Double c) {
return (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x) > 0;
}
static boolean rightOf(Point.Double p, QuadEdge e) {
return isCCW(p, e.dest(), e.orig());
}
}
// Guibas and Stolfi,"Primitives for the manipulation of general subdivisions and the computation of Voronoi diagrams"
static class QuadEdge {
QuadEdge next; // next CCW edge
QuadEdge rot; // the dual of this edge, directed from right to left
Point.Double vertex; // The vertex that this edge represents
static QuadEdge makeEdge(Point.Double o, Point.Double d) {
QuadEdge q0 = new QuadEdge();
QuadEdge q1 = new QuadEdge();
QuadEdge q2 = new QuadEdge();
QuadEdge q3 = new QuadEdge();
q0.rot = q1;
q1.rot = q2;
q2.rot = q3;
q3.rot = q0;
q0.setOnext(q0);
q1.setOnext(q3);
q2.setOnext(q2);
q3.setOnext(q1);
q0.setOrig(o);
q0.setDest(d);
return q0;
}
/**
* Creates a new QuadEdge connecting the destination of a to the origin of
* b, in such a way that all three have the same left face after the connection is complete.
*/
static QuadEdge connect(QuadEdge a, QuadEdge b) {
QuadEdge e = makeEdge(a.dest(), b.orig());
splice(e, a.lNext());
splice(e.sym(), b);
return e;
}
/**
* Splices two edges together or apart.
* Splice affects the two edge rings around the origins of a and b, and, independently, the two
* edge rings around the left faces of a and b.
* In each case, (i) if the two rings are distinct,
* Splice will combine them into one, or (ii) if the two are the same ring, Splice will break it
* into two separate pieces. Thus, Splice can be used both to attach the two edges together, and
* to break them apart.
*/
static void splice(QuadEdge a, QuadEdge b) {
QuadEdge alpha = a.oNext().rot();
QuadEdge beta = b.oNext().rot();
QuadEdge t1 = b.oNext();
QuadEdge t2 = a.oNext();
QuadEdge t3 = beta.oNext();
QuadEdge t4 = alpha.oNext();
a.setOnext(t1);
b.setOnext(t2);
alpha.setOnext(t3);
beta.setOnext(t4);
}
// Turns an edge counterclockwise inside its enclosing quadrilateral
static void swap(QuadEdge e) {
QuadEdge a = e.oPrev();
QuadEdge b = e.sym().oPrev();
splice(e, a);
splice(e.sym(), b);
splice(e, a.lNext());
splice(e.sym(), b.lNext());
e.setOrig(a.dest());
e.setDest(b.dest());
}
void delete() {
rot = null;
}
boolean isNotDeleted() {
return rot != null;
}
void setOnext(QuadEdge next) {
this.next = next;
}
QuadEdge rot() {
return rot;
}
QuadEdge sym() {
return rot.rot;
}
QuadEdge invRot() {
return rot.rot.rot;
}
QuadEdge oNext() {
return next;
}
QuadEdge oPrev() {
return rot.next.rot;
}
QuadEdge dNext() {
return sym().next.sym();
}
QuadEdge dPrev() {
return invRot().next.invRot();
}
QuadEdge lNext() {
return invRot().next.rot;
}
QuadEdge lPrev() {
return next.sym();
}
QuadEdge rNext() {
return rot.next.invRot();
}
QuadEdge rPrev() {
return sym().next;
}
void setOrig(Point.Double o) {
vertex = o;
}
void setDest(Point.Double d) {
sym().setOrig(d);
}
Point.Double orig() {
return vertex;
}
Point.Double dest() {
return sym().orig();
}
}
// visualization
Random rnd = new Random(1);
List<Point.Double> points = new ArrayList<>();
List<Point2D.Double[]> tr = Collections.emptyList();
List<Point2D.Double[]> voronoiCellPolygons = Collections.emptyList();
public DelaunayVoronoi() {
int n = 100;
for (int i = 0; i < n; i++) {
int x = rnd.nextInt(950) + 1;
int y = rnd.nextInt(700) + 1;
Point.Double c = new Point.Double(x, y);
points.add(c);
}
setContentPane(new JPanel() {
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = ((Graphics2D) g);
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2.setStroke(new BasicStroke(1));
g.setColor(Color.BLUE);
for (Object o : tr) {
Point.Double[] a = (Point.Double[]) o;
for (int i = 0; i + 1 < a.length; i++) {
g.drawLine((int) a[i].x, (int) a[i].y, (int) a[i + 1].x, (int) a[i + 1].y);
}
}
g2.setStroke(new BasicStroke(3));
g.setColor(Color.BLACK);
for (Object o : voronoiCellPolygons) {
Point.Double[] a = (Point.Double[]) o;
for (int i = 0; i + 1 < a.length; i++) {
g.drawLine((int) a[i].x, (int) a[i].y, (int) a[i + 1].x, (int) a[i + 1].y);
}
}
g.setColor(Color.RED);
for (Point.Double point : points) {
g.drawOval((int) point.x - 2, (int) point.y - 2, 5, 5);
}
}
});
setSize(new Dimension(1024, 768));
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
setVisible(true);
new Thread() {
public void run() {
while (true) {
final Point2D.Double pivot = points.get(0);
pivot.x += rnd.nextInt(4);
pivot.y += rnd.nextInt(2);
pivot.x %= 950;
pivot.y %= 700;
Set<Point.Double> uniquePoints = new HashSet<>(points);
SubDivision subdivision = new SubDivision(uniquePoints);
for (Point.Double p : uniquePoints) subdivision.insertSite(p);
tr = subdivision.getTriangleCoordinates();
voronoiCellPolygons = subdivision.getVoronoiCellPolygons();
repaint();
try {
Thread.sleep(15);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}.start();
}
public static void main(String[] args) {
new DelaunayVoronoi();
}
}