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Java example source code file (BoundaryBuilder.java)

This example Java source code file (BoundaryBuilder.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

boundaryattribute, boundarybuilder, bsptree, bsptreevisitor, characterization, nodesset, order, space, subhyperplane

The BoundaryBuilder.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;

/** Visitor building boundary shell tree.
 * <p>
 * The boundary shell is represented as {@link BoundaryAttribute boundary attributes}
 * at each internal node.
 * </p>
 * @param <S> Type of the space.
 * @since 3.4
 */
class BoundaryBuilder<S extends Space> implements BSPTreeVisitor {

    /** {@inheritDoc} */
    public Order visitOrder(BSPTree<S> node) {
        return Order.PLUS_MINUS_SUB;
    }

    /** {@inheritDoc} */
    public void visitInternalNode(BSPTree<S> node) {

        SubHyperplane<S> plusOutside = null;
        SubHyperplane<S> plusInside  = null;
        NodesSet<S>      splitters   = null;

        // characterize the cut sub-hyperplane,
        // first with respect to the plus sub-tree
        final Characterization<S> plusChar = new Characterization(node.getPlus(), node.getCut().copySelf());

        if (plusChar.touchOutside()) {
            // plusChar.outsideTouching() corresponds to a subset of the cut sub-hyperplane
            // known to have outside cells on its plus side, we want to check if parts
            // of this subset do have inside cells on their minus side
            final Characterization<S> minusChar = new Characterization(node.getMinus(), plusChar.outsideTouching());
            if (minusChar.touchInside()) {
                // this part belongs to the boundary,
                // it has the outside on its plus side and the inside on its minus side
                plusOutside = minusChar.insideTouching();
                splitters = new NodesSet<S>();
                splitters.addAll(minusChar.getInsideSplitters());
                splitters.addAll(plusChar.getOutsideSplitters());
            }
        }

        if (plusChar.touchInside()) {
            // plusChar.insideTouching() corresponds to a subset of the cut sub-hyperplane
            // known to have inside cells on its plus side, we want to check if parts
            // of this subset do have outside cells on their minus side
            final Characterization<S> minusChar = new Characterization(node.getMinus(), plusChar.insideTouching());
            if (minusChar.touchOutside()) {
                // this part belongs to the boundary,
                // it has the inside on its plus side and the outside on its minus side
                plusInside = minusChar.outsideTouching();
                if (splitters == null) {
                    splitters = new NodesSet<S>();
                }
                splitters.addAll(minusChar.getOutsideSplitters());
                splitters.addAll(plusChar.getInsideSplitters());
            }
        }

        if (splitters != null) {
            // the parent nodes are natural splitters for boundary sub-hyperplanes
            for (BSPTree<S> up = node.getParent(); up != null; up = up.getParent()) {
                splitters.add(up);
            }
        }

        // set the boundary attribute at non-leaf nodes
        node.setAttribute(new BoundaryAttribute<S>(plusOutside, plusInside, splitters));

    }

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

}

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