    001    /*
    002     * Licensed to the Apache Software Foundation (ASF) under one or more
    003     * contributor license agreements.  See the NOTICE file distributed with
    004     * this work for additional information regarding copyright ownership.
    005     * The ASF licenses this file to You under the Apache License, Version 2.0
    006     * (the "License"); you may not use this file except in compliance with
    007     * the License.  You may obtain a copy of the License at
    008     *
    009     *      http://www.apache.org/licenses/LICENSE-2.0
    010     *
    011     * Unless required by applicable law or agreed to in writing, software
    012     * distributed under the License is distributed on an "AS IS" BASIS,
    013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014     * See the License for the specific language governing permissions and
    015     * limitations under the License.
    016     */
    017    package org.apache.commons.math3.geometry.euclidean.threed;
    018
    019    import java.util.ArrayList;
    020    import java.util.List;
    021
    022    import org.apache.commons.math3.exception.MathIllegalArgumentException;
    023    import org.apache.commons.math3.geometry.euclidean.oned.Interval;
    024    import org.apache.commons.math3.geometry.euclidean.oned.IntervalsSet;
    025    import org.apache.commons.math3.geometry.euclidean.oned.Vector1D;
    026    import org.apache.commons.math3.geometry.partitioning.Region.Location;
    027
    028    /** This class represents a subset of a {@link Line}.
    029     * @version $Id: SubLine.java 1416643 2012-12-03 19:37:14Z tn $
    030     * @since 3.0
    031     */
    032    public class SubLine {
    033
    034        /** Underlying line. */
    035        private final Line line;
    036
    037        /** Remaining region of the hyperplane. */
    038        private final IntervalsSet remainingRegion;
    039
    040        /** Simple constructor.
    041         * @param line underlying line
    042         * @param remainingRegion remaining region of the line
    043         */
    044        public SubLine(final Line line, final IntervalsSet remainingRegion) {
    045            this.line            = line;
    046            this.remainingRegion = remainingRegion;
    047        }
    048
    049        /** Create a sub-line from two endpoints.
    050         * @param start start point
    051         * @param end end point
    052         * @exception MathIllegalArgumentException if the points are equal
    053         */
    054        public SubLine(final Vector3D start, final Vector3D end)
    055            throws MathIllegalArgumentException {
    056            this(new Line(start, end), buildIntervalSet(start, end));
    057        }
    058
    059        /** Create a sub-line from a segment.
    060         * @param segment single segment forming the sub-line
    061         * @exception MathIllegalArgumentException if the segment endpoints are equal
    062         */
    063        public SubLine(final Segment segment) throws MathIllegalArgumentException {
    064            this(segment.getLine(), buildIntervalSet(segment.getStart(), segment.getEnd()));
    065        }
    066
    067        /** Get the endpoints of the sub-line.
    068         * <p>
    069         * A subline may be any arbitrary number of disjoints segments, so the endpoints
    070         * are provided as a list of endpoint pairs. Each element of the list represents
    071         * one segment, and each segment contains a start point at index 0 and an end point
    072         * at index 1. If the sub-line is unbounded in the negative infinity direction,
    073         * the start point of the first segment will have infinite coordinates. If the
    074         * sub-line is unbounded in the positive infinity direction, the end point of the
    075         * last segment will have infinite coordinates. So a sub-line covering the whole
    076         * line will contain just one row and both elements of this row will have infinite
    077         * coordinates. If the sub-line is empty, the returned list will contain 0 segments.
    078         * </p>
    079         * @return list of segments endpoints
    080         */
    081        public List<Segment> getSegments() {
    082
    083            final List<Interval> list = remainingRegion.asList();
    084            final List<Segment> segments = new ArrayList<Segment>();
    085
    086            for (final Interval interval : list) {
    087                final Vector3D start = line.toSpace(new Vector1D(interval.getInf()));
    088                final Vector3D end   = line.toSpace(new Vector1D(interval.getSup()));
    089                segments.add(new Segment(start, end, line));
    090            }
    091
    092            return segments;
    093
    094        }
    095
    096        /** Get the intersection of the instance and another sub-line.
    097         * <p>
    098         * This method is related to the {@link Line#intersection(Line)
    099         * intersection} method in the {@link Line Line} class, but in addition
    100         * to compute the point along infinite lines, it also checks the point
    101         * lies on both sub-line ranges.
    102         * </p>
    103         * @param subLine other sub-line which may intersect instance
    104         * @param includeEndPoints if true, endpoints are considered to belong to
    105         * instance (i.e. they are closed sets) and may be returned, otherwise endpoints
    106         * are considered to not belong to instance (i.e. they are open sets) and intersection
    107         * occurring on endpoints lead to null being returned
    108         * @return the intersection point if there is one, null if the sub-lines don't intersect
    109         */
    110        public Vector3D intersection(final SubLine subLine, final boolean includeEndPoints) {
    111
    112            // compute the intersection on infinite line
    113            Vector3D v1D = line.intersection(subLine.line);
    114
    115            // check location of point with respect to first sub-line
    116            Location loc1 = remainingRegion.checkPoint(line.toSubSpace(v1D));
    117
    118            // check location of point with respect to second sub-line
    119            Location loc2 = subLine.remainingRegion.checkPoint(subLine.line.toSubSpace(v1D));
    120
    121            if (includeEndPoints) {
    122                return ((loc1 != Location.OUTSIDE) && (loc2 != Location.OUTSIDE)) ? v1D : null;
    123            } else {
    124                return ((loc1 == Location.INSIDE) && (loc2 == Location.INSIDE)) ? v1D : null;
    125            }
    126
    127        }
    128
    129        /** Build an interval set from two points.
    130         * @param start start point
    131         * @param end end point
    132         * @return an interval set
    133         * @exception MathIllegalArgumentException if the points are equal
    134         */
    135        private static IntervalsSet buildIntervalSet(final Vector3D start, final Vector3D end)
    136            throws MathIllegalArgumentException {
    137            final Line line = new Line(start, end);
    138            return new IntervalsSet(line.toSubSpace(start).getX(),
    139                                    line.toSubSpace(end).getX());
    140        }
    141
    142    }