View Javadoc

    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  }