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.core; 18 19 /** Interface representing a region in a space. A region partitions a space 20 * into sets of points lying on the inside, outside, and boundary. 21 * @param <P> Point implementation type 22 */ 23 public interface Region<P extends Point<P>> extends Sized { 24 25 /** Return true if the region spans the entire space. In other words, 26 * a region is full if no points in the space are classified as 27 * {@link RegionLocation#OUTSIDE outside}. 28 * @return true if the region spans the entire space 29 */ 30 boolean isFull(); 31 32 /** Return true if the region is completely empty, ie all points in 33 * the space are classified as {@link RegionLocation#OUTSIDE outside}. 34 * @return true if the region is empty 35 */ 36 boolean isEmpty(); 37 38 /** Get the size of the boundary of the region. The size is a value in 39 * the {@code d-1} dimension space. For example, in Euclidean space, 40 * this will be a length in 2D and an area in 3D. 41 * @return the size of the boundary of the region 42 */ 43 double getBoundarySize(); 44 45 /** Get the centroid, or geometric center, of the region or null if no centroid 46 * exists or one exists but is not unique. A centroid will not exist for empty or 47 * infinite regions. 48 * 49 * <p>The centroid of a geometric object is defined as the mean position of 50 * all points in the object, including interior points, vertices, and other points 51 * lying on the boundary. If a physical object has a uniform density, then its center 52 * of mass is the same as its geometric centroid. 53 * </p> 54 * @return the centroid of the region or null if no unique centroid exists 55 * @see <a href="https://en.wikipedia.org/wiki/Centroid">Centroid</a> 56 */ 57 P getCentroid(); 58 59 /** Classify the given point with respect to the region. 60 * @param pt the point to classify 61 * @return the location of the point with respect to the region 62 */ 63 RegionLocation classify(P pt); 64 65 /** Return true if the given point is on the inside or boundary 66 * of the region. 67 * @param pt the point to test 68 * @return true if the point is on the inside or boundary of the region 69 */ 70 default boolean contains(final P pt) { 71 final RegionLocation location = classify(pt); 72 return location != null && location != RegionLocation.OUTSIDE; 73 } 74 75 /** Project a point onto the boundary of the region. Null is returned if 76 * the region contains no boundaries (ie, is either {@link #isFull() full} 77 * or {@link #isEmpty() empty}). 78 * @param pt pt to project 79 * @return projection of the point on the boundary of the region or null 80 * if the region does not contain any boundaries 81 */ 82 P project(P pt); 83 }