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 * http://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 package org.apache.commons.geometry.spherical.twod;
18
19 import java.util.Collection;
20 import java.util.List;
21
22 /** Great arc connector that selects between multiple connection options
23 * based on the resulting interior angle. An interior angle in this
24 * case is the angle created between an incoming arc and an outgoing arc
25 * as measured on the minus (interior) side of the incoming arc. If looking
26 * along the direction of the incoming arc, smaller interior angles
27 * point more to the left and larger ones point more to the right.
28 *
29 * <p>This class provides two concrete implementations: {@link Maximize} and
30 * {@link Minimize}, which choose connections with the largest or smallest interior
31 * angles respectively.
32 * </p>
33 */
34 public abstract class InteriorAngleGreatArcConnector extends AbstractGreatArcConnector {
35 /** {@inheritDoc} */
36 @Override
37 protected ConnectableGreatArc selectConnection(final ConnectableGreatArc incoming,
38 final List<ConnectableGreatArc> outgoing) {
39
40 // search for the best connection
41 final GreatCircle circle = incoming.getArc().getCircle();
42
43 double selectedInteriorAngle = Double.POSITIVE_INFINITY;
44 ConnectableGreatArc selected = null;
45
46 for (final ConnectableGreatArc candidate : outgoing) {
47 final double interiorAngle = Math.PI - circle.angle(candidate.getArc().getCircle(),
48 incoming.getArc().getEndPoint());
49
50 if (selected == null || isBetterAngle(interiorAngle, selectedInteriorAngle)) {
51 selectedInteriorAngle = interiorAngle;
52 selected = candidate;
53 }
54 }
55
56 return selected;
57 }
58
59 /** Return true if {@code newAngle} represents a better interior angle than {@code previousAngle}.
60 * @param newAngle the new angle under consideration
61 * @param previousAngle the previous best angle
62 * @return true if {@code newAngle} represents a better interior angle than {@code previousAngle}
63 */
64 protected abstract boolean isBetterAngle(double newAngle, double previousAngle);
65
66 /** Convenience method for connecting a set of arcs with interior angles maximized
67 * when possible. This method is equivalent to {@code new Maximize().connect(segments)}.
68 * @param arcs arcs to connect
69 * @return a list of connected arc paths
70 * @see Maximize
71 */
72 public static List<GreatArcPath> connectMaximized(final Collection<GreatArc> arcs) {
73 return new Maximize().connectAll(arcs);
74 }
75
76 /** Convenience method for connecting a set of line segments with interior angles minimized
77 * when possible. This method is equivalent to {@code new Minimize().connect(segments)}.
78 * @param arcs arcs to connect
79 * @return a list of connected arc paths
80 * @see Minimize
81 */
82 public static List<GreatArcPath> connectMinimized(final Collection<GreatArc> arcs) {
83 return new Minimize().connectAll(arcs);
84 }
85
86 /** Implementation of {@link InteriorAngleGreatArcConnector} that chooses arc
87 * connections that produce the largest interior angles. Another way to visualize this is
88 * that when presented multiple connection options for a given arc, this class will
89 * choose the option that points most to the right when viewed in the direction of the incoming
90 * arc.
91 */
92 public static class Maximize extends InteriorAngleGreatArcConnector {
93 /** {@inheritDoc} */
94 @Override
95 protected boolean isBetterAngle(final double newAngle, final double previousAngle) {
96 return newAngle > previousAngle;
97 }
98 }
99
100 /** Implementation of {@link InteriorAngleGreatArcConnector} that chooses arc
101 * connections that produce the smallest interior angles. Another way to visualize this is
102 * that when presented multiple connection options for a given arc, this class will
103 * choose the option that points most to the left when viewed in the direction of the incoming
104 * arc.
105 */
106 public static class Minimize extends InteriorAngleGreatArcConnector {
107 /** {@inheritDoc} */
108 @Override
109 protected boolean isBetterAngle(final double newAngle, final double previousAngle) {
110 return newAngle < previousAngle;
111 }
112 }
113 }