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Java example source code file (EdgesBuilder.java)

This example Java source code file (EdgesBuilder.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

arc, boundaryattribute, bsptree, circle, edge, edgesbuilder, identityhashmap, list, mathillegalstateexception, order, subcircle, suppresswarnings, util, vector3d, vertex

The EdgesBuilder.java Java example source code

 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *      http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.
package org.apache.commons.math3.geometry.spherical.twod;

import java.util.ArrayList;
import java.util.IdentityHashMap;
import java.util.List;
import java.util.Map;

import org.apache.commons.math3.exception.MathIllegalStateException;
import org.apache.commons.math3.exception.util.LocalizedFormats;
import org.apache.commons.math3.geometry.euclidean.threed.Vector3D;
import org.apache.commons.math3.geometry.partitioning.BSPTree;
import org.apache.commons.math3.geometry.partitioning.BSPTreeVisitor;
import org.apache.commons.math3.geometry.partitioning.BoundaryAttribute;
import org.apache.commons.math3.geometry.spherical.oned.Arc;
import org.apache.commons.math3.geometry.spherical.oned.ArcsSet;
import org.apache.commons.math3.geometry.spherical.oned.S1Point;

/** Visitor building edges.
 * @since 3.3
class EdgesBuilder implements BSPTreeVisitor<Sphere2D> {

    /** Root of the tree. */
    private final BSPTree<Sphere2D> root;

    /** Tolerance below which points are consider to be identical. */
    private final double tolerance;

    /** Built edges and their associated nodes. */
    private final Map<Edge, BSPTree edgeToNode;

    /** Reversed map. */
    private final Map<BSPTree> nodeToEdgesList;

    /** Simple constructor.
     * @param root tree root
     * @param tolerance below which points are consider to be identical
    EdgesBuilder(final BSPTree<Sphere2D> root, final double tolerance) {
        this.root            = root;
        this.tolerance       = tolerance;
        this.edgeToNode      = new IdentityHashMap<Edge, BSPTree();
        this.nodeToEdgesList = new IdentityHashMap<BSPTree>();

    /** {@inheritDoc} */
    public Order visitOrder(final BSPTree<Sphere2D> node) {
        return Order.MINUS_SUB_PLUS;

    /** {@inheritDoc} */
    public void visitInternalNode(final BSPTree<Sphere2D> node) {
        nodeToEdgesList.put(node, new ArrayList<Edge>());
        final BoundaryAttribute<Sphere2D> attribute = (BoundaryAttribute) node.getAttribute();
        if (attribute.getPlusOutside() != null) {
            addContribution((SubCircle) attribute.getPlusOutside(), false, node);
        if (attribute.getPlusInside() != null) {
            addContribution((SubCircle) attribute.getPlusInside(), true, node);

    /** {@inheritDoc} */
    public void visitLeafNode(final BSPTree<Sphere2D> node) {

    /** Add the contribution of a boundary edge.
     * @param sub boundary facet
     * @param reversed if true, the facet has the inside on its plus side
     * @param node node to which the edge belongs
    private void addContribution(final SubCircle sub, final boolean reversed,
                                 final BSPTree<Sphere2D> node) {
        final Circle circle  = (Circle) sub.getHyperplane();
        final List<Arc> arcs = ((ArcsSet) sub.getRemainingRegion()).asList();
        for (final Arc a : arcs) {
            final Vertex start = new Vertex((S2Point) circle.toSpace(new S1Point(a.getInf())));
            final Vertex end   = new Vertex((S2Point) circle.toSpace(new S1Point(a.getSup())));
            final Edge edge;
            if (reversed) {
                edge = new Edge(end, start, a.getSize(), circle.getReverse());
            } else {
                edge = new Edge(start, end, a.getSize(), circle);
            edgeToNode.put(edge, node);

    /** Get the edge that should naturally follow another one.
     * @param previous edge to be continued
     * @return other edge, starting where the previous one ends (they
     * have not been connected yet)
     * @exception MathIllegalStateException if there is not a single other edge
    private Edge getFollowingEdge(final Edge previous)
        throws MathIllegalStateException {

        // get the candidate nodes
        final S2Point point = previous.getEnd().getLocation();
        final List<BSPTree candidates = root.getCloseCuts(point, tolerance);

        // the following edge we are looking for must start from one of the candidates nodes
        double closest = tolerance;
        Edge following = null;
        for (final BSPTree<Sphere2D> node : candidates) {
            for (final Edge edge : nodeToEdgesList.get(node)) {
                if (edge != previous && edge.getStart().getIncoming() == null) {
                    final Vector3D edgeStart = edge.getStart().getLocation().getVector();
                    final double gap         = Vector3D.angle(point.getVector(), edgeStart);
                    if (gap <= closest) {
                        closest   = gap;
                        following = edge;

        if (following == null) {
            final Vector3D previousStart = previous.getStart().getLocation().getVector();
            if (Vector3D.angle(point.getVector(), previousStart) <= tolerance) {
                // the edge connects back to itself
                return previous;

            // this should never happen
            throw new MathIllegalStateException(LocalizedFormats.OUTLINE_BOUNDARY_LOOP_OPEN);


        return following;


    /** Get the boundary edges.
     * @return boundary edges
     * @exception MathIllegalStateException if there is not a single other edge
    public List<Edge> getEdges() throws MathIllegalStateException {

        // connect the edges
        for (final Edge previous : edgeToNode.keySet()) {

        return new ArrayList<Edge>(edgeToNode.keySet());



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