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    }