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 */ 017package org.apache.commons.geometry.spherical.twod; 018 019import java.util.Collection; 020import java.util.List; 021 022/** Great arc connector that selects between multiple connection options 023 * based on the resulting interior angle. An interior angle in this 024 * case is the angle created between an incoming arc and an outgoing arc 025 * as measured on the minus (interior) side of the incoming arc. If looking 026 * along the direction of the incoming arc, smaller interior angles 027 * point more to the left and larger ones point more to the right. 028 * 029 * <p>This class provides two concrete implementations: {@link Maximize} and 030 * {@link Minimize}, which choose connections with the largest or smallest interior 031 * angles respectively. 032 * </p> 033 */ 034public abstract class InteriorAngleGreatArcConnector extends AbstractGreatArcConnector { 035 /** {@inheritDoc} */ 036 @Override 037 protected ConnectableGreatArc selectConnection(final ConnectableGreatArc incoming, 038 final List<ConnectableGreatArc> outgoing) { 039 040 // search for the best connection 041 final GreatCircle circle = incoming.getArc().getCircle(); 042 043 double selectedInteriorAngle = Double.POSITIVE_INFINITY; 044 ConnectableGreatArc selected = null; 045 046 for (final ConnectableGreatArc candidate : outgoing) { 047 final double interiorAngle = Math.PI - circle.angle(candidate.getArc().getCircle(), 048 incoming.getArc().getEndPoint()); 049 050 if (selected == null || isBetterAngle(interiorAngle, selectedInteriorAngle)) { 051 selectedInteriorAngle = interiorAngle; 052 selected = candidate; 053 } 054 } 055 056 return selected; 057 } 058 059 /** Return true if {@code newAngle} represents a better interior angle than {@code previousAngle}. 060 * @param newAngle the new angle under consideration 061 * @param previousAngle the previous best angle 062 * @return true if {@code newAngle} represents a better interior angle than {@code previousAngle} 063 */ 064 protected abstract boolean isBetterAngle(double newAngle, double previousAngle); 065 066 /** Convenience method for connecting a set of arcs with interior angles maximized 067 * when possible. This method is equivalent to {@code new Maximize().connect(segments)}. 068 * @param arcs arcs to connect 069 * @return a list of connected arc paths 070 * @see Maximize 071 */ 072 public static List<GreatArcPath> connectMaximized(final Collection<GreatArc> arcs) { 073 return new Maximize().connectAll(arcs); 074 } 075 076 /** Convenience method for connecting a set of line segments with interior angles minimized 077 * when possible. This method is equivalent to {@code new Minimize().connect(segments)}. 078 * @param arcs arcs to connect 079 * @return a list of connected arc paths 080 * @see Minimize 081 */ 082 public static List<GreatArcPath> connectMinimized(final Collection<GreatArc> arcs) { 083 return new Minimize().connectAll(arcs); 084 } 085 086 /** Implementation of {@link InteriorAngleGreatArcConnector} that chooses arc 087 * connections that produce the largest interior angles. Another way to visualize this is 088 * that when presented multiple connection options for a given arc, this class will 089 * choose the option that points most to the right when viewed in the direction of the incoming 090 * arc. 091 */ 092 public static class Maximize extends InteriorAngleGreatArcConnector { 093 /** {@inheritDoc} */ 094 @Override 095 protected boolean isBetterAngle(final double newAngle, final double previousAngle) { 096 return newAngle > previousAngle; 097 } 098 } 099 100 /** 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}