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Java example source code file (InsideFinder.java)

This example Java source code file (InsideFinder.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

boolean, both, bsptree, hyperplane, insidefinder, minus, plus, region, space, subhyperplane

The InsideFinder.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,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.math3.geometry.partitioning;

import org.apache.commons.math3.geometry.Space;

/** Utility class checking if inside nodes can be found
 * on the plus and minus sides of an hyperplane.
 * @param <S> Type of the space.
 * @since 3.4
 */
class InsideFinder<S extends Space> {

    /** Region on which to operate. */
    private final Region<S> region;

    /** Indicator of inside leaf nodes found on the plus side. */
    private boolean plusFound;

    /** Indicator of inside leaf nodes found on the plus side. */
    private boolean minusFound;

    /** Simple constructor.
     * @param region region on which to operate
     */
    InsideFinder(final Region<S> region) {
        this.region = region;
        plusFound  = false;
        minusFound = false;
    }

    /** Search recursively for inside leaf nodes on each side of the given hyperplane.

     * <p>The algorithm used here is directly derived from the one
     * described in section III (<i>Binary Partitioning of a BSP
     * Tree</i>) of the Bruce Naylor, John Amanatides and William
     * Thibault paper <a
     * href="http://www.cs.yorku.ca/~amana/research/bsptSetOp.pdf">Merging
     * BSP Trees Yields Polyhedral Set Operations</a> Proc. Siggraph
     * '90, Computer Graphics 24(4), August 1990, pp 115-124, published
     * by the Association for Computing Machinery (ACM)..</p>

     * @param node current BSP tree node
     * @param sub sub-hyperplane
     */
    public void recurseSides(final BSPTree<S> node, final SubHyperplane sub) {

        if (node.getCut() == null) {
            if ((Boolean) node.getAttribute()) {
                // this is an inside cell expanding across the hyperplane
                plusFound  = true;
                minusFound = true;
            }
            return;
        }

        final Hyperplane<S> hyperplane = node.getCut().getHyperplane();
        final SubHyperplane.SplitSubHyperplane<S> split = sub.split(hyperplane);
        switch (split.getSide()) {
        case PLUS :
            // the sub-hyperplane is entirely in the plus sub-tree
            if (node.getCut().split(sub.getHyperplane()).getSide() == Side.PLUS) {
                if (!region.isEmpty(node.getMinus())) {
                    plusFound  = true;
                }
            } else {
                if (!region.isEmpty(node.getMinus())) {
                    minusFound = true;
                }
            }
            if (!(plusFound && minusFound)) {
                recurseSides(node.getPlus(), sub);
            }
            break;
        case MINUS :
            // the sub-hyperplane is entirely in the minus sub-tree
            if (node.getCut().split(sub.getHyperplane()).getSide() == Side.PLUS) {
                if (!region.isEmpty(node.getPlus())) {
                    plusFound  = true;
                }
            } else {
                if (!region.isEmpty(node.getPlus())) {
                    minusFound = true;
                }
            }
            if (!(plusFound && minusFound)) {
                recurseSides(node.getMinus(), sub);
            }
            break;
        case BOTH :
            // the sub-hyperplane extends in both sub-trees

            // explore first the plus sub-tree
            recurseSides(node.getPlus(), split.getPlus());

            // if needed, explore the minus sub-tree
            if (!(plusFound && minusFound)) {
                recurseSides(node.getMinus(), split.getMinus());
            }
            break;
        default :
            // the sub-hyperplane and the cut sub-hyperplane share the same hyperplane
            if (node.getCut().getHyperplane().sameOrientationAs(sub.getHyperplane())) {
                if ((node.getPlus().getCut() != null) || ((Boolean) node.getPlus().getAttribute())) {
                    plusFound  = true;
                }
                if ((node.getMinus().getCut() != null) || ((Boolean) node.getMinus().getAttribute())) {
                    minusFound = true;
                }
            } else {
                if ((node.getPlus().getCut() != null) || ((Boolean) node.getPlus().getAttribute())) {
                    minusFound = true;
                }
                if ((node.getMinus().getCut() != null) || ((Boolean) node.getMinus().getAttribute())) {
                    plusFound  = true;
                }
            }
        }

    }

    /** Check if inside leaf nodes have been found on the plus side.
     * @return true if inside leaf nodes have been found on the plus side
     */
    public boolean plusFound() {
        return plusFound;
    }

    /** Check if inside leaf nodes have been found on the minus side.
     * @return true if inside leaf nodes have been found on the minus side
     */
    public boolean minusFound() {
        return minusFound;
    }

}

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