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 }