1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * https://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 /*
19 * This is not the original file distributed by the Apache Software Foundation
20 * It has been modified by the Hipparchus project
21 */
22 package org.hipparchus.geometry.euclidean.twod;
23
24 import org.hipparchus.geometry.Point;
25 import org.hipparchus.util.FastMath;
26
27 /** Simple container for a two-points segment.
28 */
29 public class Segment {
30
31 /** Start point of the segment. */
32 private final Vector2D start;
33
34 /** End point of the segment. */
35 private final Vector2D end;
36
37 /** Line containing the segment. */
38 private final Line line;
39
40 /** Build a segment.
41 * @param start start point of the segment
42 * @param end end point of the segment
43 * @param tolerance of the line.
44 */
45 public Segment(final Vector2D start, final Vector2D end, final double tolerance) {
46 this(start, end, new Line(start, end, tolerance));
47 }
48
49 /** Build a segment.
50 * @param start start point of the segment
51 * @param end end point of the segment
52 * @param line line containing the segment
53 */
54 public Segment(final Vector2D start, final Vector2D end, final Line line) {
55 this.start = start;
56 this.end = end;
57 this.line = line;
58 }
59
60 /** Get the start point of the segment.
61 * @return start point of the segment
62 */
63 public Vector2D getStart() {
64 return start;
65 }
66
67 /** Get the end point of the segment.
68 * @return end point of the segment
69 */
70 public Vector2D getEnd() {
71 return end;
72 }
73
74 /** Get the line containing the segment.
75 * @return line containing the segment
76 */
77 public Line getLine() {
78 return line;
79 }
80
81 /**
82 * Get the length of the line segment.
83 *
84 * @return line segment length.
85 */
86 public double getLength() {
87 return getEnd().distance(getStart());
88 }
89
90 /** Calculates the shortest distance from a point to this line segment.
91 * <p>
92 * If the perpendicular extension from the point to the line does not
93 * cross in the bounds of the line segment, the shortest distance to
94 * the two end points will be returned.
95 * </p>
96 *
97 * Algorithm adapted from:
98 * <a href="http://www.codeguru.com/forum/printthread.php?s=cc8cf0596231f9a7dba4da6e77c29db3&t=194400&pp=15&page=1">
99 * Thread @ Codeguru</a>
100 *
101 * @param p to check
102 * @return distance between the instance and the point
103 */
104 public double distance(final Vector2D p) {
105 final double deltaX = end.getX() - start.getX();
106 final double deltaY = end.getY() - start.getY();
107
108 final double r = ((p.getX() - start.getX()) * deltaX + (p.getY() - start.getY()) * deltaY) /
109 (deltaX * deltaX + deltaY * deltaY);
110
111 // r == 0 => P = startPt
112 // r == 1 => P = endPt
113 // r < 0 => P is on the backward extension of the segment
114 // r > 1 => P is on the forward extension of the segment
115 // 0 < r < 1 => P is on the segment
116
117 // if point isn't on the line segment, just return the shortest distance to the end points
118 if (r < 0 || r > 1) {
119 final double dist1 = getStart().distance((Point<Euclidean2D>) p);
120 final double dist2 = getEnd().distance((Point<Euclidean2D>) p);
121
122 return FastMath.min(dist1, dist2);
123 }
124 else {
125 // find point on line and see if it is in the line segment
126 final double px = start.getX() + r * deltaX;
127 final double py = start.getY() + r * deltaY;
128
129 final Vector2D interPt = new Vector2D(px, py);
130 return interPt.distance((Point<Euclidean2D>) p);
131 }
132 }
133 }