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.core; 018 019/** Interface representing a region in a space. A region partitions a space 020 * into sets of points lying on the inside, outside, and boundary. 021 * @param <P> Point implementation type 022 */ 023public interface Region<P extends Point<P>> extends Sized { 024 025 /** Return true if the region spans the entire space. In other words, 026 * a region is full if no points in the space are classified as 027 * {@link RegionLocation#OUTSIDE outside}. 028 * @return true if the region spans the entire space 029 */ 030 boolean isFull(); 031 032 /** Return true if the region is completely empty, ie all points in 033 * the space are classified as {@link RegionLocation#OUTSIDE outside}. 034 * @return true if the region is empty 035 */ 036 boolean isEmpty(); 037 038 /** Get the size of the boundary of the region. The size is a value in 039 * the {@code d-1} dimension space. For example, in Euclidean space, 040 * this will be a length in 2D and an area in 3D. 041 * @return the size of the boundary of the region 042 */ 043 double getBoundarySize(); 044 045 /** Get the centroid, or geometric center, of the region or null if no centroid 046 * exists or one exists but is not unique. A centroid will not exist for empty or 047 * infinite regions. 048 * 049 * <p>The centroid of a geometric object is defined as the mean position of 050 * all points in the object, including interior points, vertices, and other points 051 * lying on the boundary. If a physical object has a uniform density, then its center 052 * of mass is the same as its geometric centroid. 053 * </p> 054 * @return the centroid of the region or null if no unique centroid exists 055 * @see <a href="https://en.wikipedia.org/wiki/Centroid">Centroid</a> 056 */ 057 P getCentroid(); 058 059 /** Classify the given point with respect to the region. 060 * @param pt the point to classify 061 * @return the location of the point with respect to the region 062 */ 063 RegionLocation classify(P pt); 064 065 /** Return true if the given point is on the inside or boundary 066 * of the region. 067 * @param pt the point to test 068 * @return true if the point is on the inside or boundary of the region 069 */ 070 default boolean contains(final P pt) { 071 final RegionLocation location = classify(pt); 072 return location != null && location != RegionLocation.OUTSIDE; 073 } 074 075 /** Project a point onto the boundary of the region. Null is returned if 076 * the region contains no boundaries (ie, is either {@link #isFull() full} 077 * or {@link #isEmpty() empty}). 078 * @param pt pt to project 079 * @return projection of the point on the boundary of the region or null 080 * if the region does not contain any boundaries 081 */ 082 P project(P pt); 083}