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Java example source code file (BoundaryProjector.java)

This example Java source code file (BoundaryProjector.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

arraylist, boundaryattribute, boundaryprojection, boundaryprojector, bsptree, embedding, hyperplane, list, order, point, region, space, suppresswarnings, util

The BoundaryProjector.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 java.util.ArrayList;
import java.util.List;

import org.apache.commons.math3.geometry.Point;
import org.apache.commons.math3.geometry.Space;
import org.apache.commons.math3.geometry.partitioning.Region.Location;
import org.apache.commons.math3.util.FastMath;

/** Local tree visitor to compute projection on boundary.
 * @param <S> Type of the space.
 * @param <T> Type of the sub-space.
 * @since 3.3
 */
class BoundaryProjector<S extends Space, T extends Space> implements BSPTreeVisitor {

    /** Original point. */
    private final Point<S> original;

    /** Current best projected point. */
    private Point<S> projected;

    /** Leaf node closest to the test point. */
    private BSPTree<S> leaf;

    /** Current offset. */
    private double offset;

    /** Simple constructor.
     * @param original original point
     */
    BoundaryProjector(final Point<S> original) {
        this.original  = original;
        this.projected = null;
        this.leaf      = null;
        this.offset    = Double.POSITIVE_INFINITY;
    }

    /** {@inheritDoc} */
    public Order visitOrder(final BSPTree<S> node) {
        // we want to visit the tree so that the first encountered
        // leaf is the one closest to the test point
        if (node.getCut().getHyperplane().getOffset(original) <= 0) {
            return Order.MINUS_SUB_PLUS;
        } else {
            return Order.PLUS_SUB_MINUS;
        }
    }

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

        // project the point on the cut sub-hyperplane
        final Hyperplane<S> hyperplane = node.getCut().getHyperplane();
        final double signedOffset = hyperplane.getOffset(original);
        if (FastMath.abs(signedOffset) < offset) {

            // project point
            final Point<S> regular = hyperplane.project(original);

            // get boundary parts
            final List<Region boundaryParts = boundaryRegions(node);

            // check if regular projection really belongs to the boundary
            boolean regularFound = false;
            for (final Region<T> part : boundaryParts) {
                if (!regularFound && belongsToPart(regular, hyperplane, part)) {
                    // the projected point lies in the boundary
                    projected    = regular;
                    offset       = FastMath.abs(signedOffset);
                    regularFound = true;
                }
            }

            if (!regularFound) {
                // the regular projected point is not on boundary,
                // so we have to check further if a singular point
                // (i.e. a vertex in 2D case) is a possible projection
                for (final Region<T> part : boundaryParts) {
                    final Point<S> spI = singularProjection(regular, hyperplane, part);
                    if (spI != null) {
                        final double distance = original.distance(spI);
                        if (distance < offset) {
                            projected = spI;
                            offset    = distance;
                        }
                    }
                }

            }

        }

    }

    /** {@inheritDoc} */
    public void visitLeafNode(final BSPTree<S> node) {
        if (leaf == null) {
            // this is the first leaf we visit,
            // it is the closest one to the original point
            leaf = node;
        }
    }

    /** Get the projection.
     * @return projection
     */
    public BoundaryProjection<S> getProjection() {

        // fix offset sign
        offset = FastMath.copySign(offset, (Boolean) leaf.getAttribute() ? -1 : +1);

        return new BoundaryProjection<S>(original, projected, offset);

    }

    /** Extract the regions of the boundary on an internal node.
     * @param node internal node
     * @return regions in the node sub-hyperplane
     */
    private List<Region boundaryRegions(final BSPTree node) {

        final List<Region regions = new ArrayList>(2);

        @SuppressWarnings("unchecked")
        final BoundaryAttribute<S> ba = (BoundaryAttribute) node.getAttribute();
        addRegion(ba.getPlusInside(),  regions);
        addRegion(ba.getPlusOutside(), regions);

        return regions;

    }

    /** Add a boundary region to a list.
     * @param sub sub-hyperplane defining the region
     * @param list to fill up
     */
    private void addRegion(final SubHyperplane<S> sub, final List> list) {
        if (sub != null) {
            @SuppressWarnings("unchecked")
            final Region<T> region = ((AbstractSubHyperplane) sub).getRemainingRegion();
            if (region != null) {
                list.add(region);
            }
        }
    }

    /** Check if a projected point lies on a boundary part.
     * @param point projected point to check
     * @param hyperplane hyperplane into which the point was projected
     * @param part boundary part
     * @return true if point lies on the boundary part
     */
    private boolean belongsToPart(final Point<S> point, final Hyperplane hyperplane,
                                  final Region<T> part) {

        // there is a non-null sub-space, we can dive into smaller dimensions
        @SuppressWarnings("unchecked")
        final Embedding<S, T> embedding = (Embedding) hyperplane;
        return part.checkPoint(embedding.toSubSpace(point)) != Location.OUTSIDE;

    }

    /** Get the projection to the closest boundary singular point.
     * @param point projected point to check
     * @param hyperplane hyperplane into which the point was projected
     * @param part boundary part
     * @return projection to a singular point of boundary part (may be null)
     */
    private Point<S> singularProjection(final Point point, final Hyperplane hyperplane,
                                        final Region<T> part) {

        // there is a non-null sub-space, we can dive into smaller dimensions
        @SuppressWarnings("unchecked")
        final Embedding<S, T> embedding = (Embedding) hyperplane;
        final BoundaryProjection<T> bp = part.projectToBoundary(embedding.toSubSpace(point));

        // back to initial dimension
        return (bp.getProjected() == null) ? null : embedding.toSpace(bp.getProjected());

    }

}

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