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.math3.geometry.partitioning;
18 
19 import org.apache.commons.math3.geometry.Space;
20 
21 /** This interface represents the remaining parts of an hyperplane after
22  * other parts have been chopped off.
23 
24  * <p>sub-hyperplanes are obtained when parts of an {@link
25  * Hyperplane hyperplane} are chopped off by other hyperplanes that
26  * intersect it. The remaining part is a convex region. Such objects
27  * appear in {@link BSPTree BSP trees} as the intersection of a cut
28  * hyperplane with the convex region which it splits, the chopping
29  * hyperplanes are the cut hyperplanes closer to the tree root.</p>
30 
31  * <p>
32  * Note that this interface is <em>not</em> intended to be implemented
33  * by Apache Commons Math users, it is only intended to be implemented
34  * within the library itself. New methods may be added even for minor
35  * versions, which breaks compatibility for external implementations.
36  * </p>
37 
38  * @param <S> Type of the embedding space.
39 
40  * @since 3.0
41  */
42 public interface SubHyperplane<S extends Space> {
43 
44     /** Copy the instance.
45      * <p>The instance created is completely independent of the original
46      * one. A deep copy is used, none of the underlying objects are
47      * shared (except for the nodes attributes and immutable
48      * objects).</p>
49      * @return a new sub-hyperplane, copy of the instance
50      */
copySelf()51     SubHyperplane<S> copySelf();
52 
53     /** Get the underlying hyperplane.
54      * @return underlying hyperplane
55      */
getHyperplane()56     Hyperplane<S> getHyperplane();
57 
58     /** Check if the instance is empty.
59      * @return true if the instance is empty
60      */
isEmpty()61     boolean isEmpty();
62 
63     /** Get the size of the instance.
64      * @return the size of the instance (this is a length in 1D, an area
65      * in 2D, a volume in 3D ...)
66      */
getSize()67     double getSize();
68 
69     /** Compute the relative position of the instance with respect
70      * to an hyperplane.
71      * @param hyperplane hyperplane to check instance against
72      * @return one of {@link Side#PLUS}, {@link Side#MINUS}, {@link Side#BOTH},
73      * {@link Side#HYPER}
74      * @deprecated as of 3.6, replaced with {@link #split(Hyperplane)}.{@link SplitSubHyperplane#getSide()}
75      */
76     @Deprecated
side(Hyperplane<S> hyperplane)77     Side side(Hyperplane<S> hyperplane);
78 
79     /** Split the instance in two parts by an hyperplane.
80      * @param hyperplane splitting hyperplane
81      * @return an object containing both the part of the instance
82      * on the plus side of the hyperplane and the part of the
83      * instance on the minus side of the hyperplane
84      */
split(Hyperplane<S> hyperplane)85     SplitSubHyperplane<S> split(Hyperplane<S> hyperplane);
86 
87     /** Compute the union of the instance and another sub-hyperplane.
88      * @param other other sub-hyperplane to union (<em>must</em> be in the
89      * same hyperplane as the instance)
90      * @return a new sub-hyperplane, union of the instance and other
91      */
reunite(SubHyperplane<S> other)92     SubHyperplane<S> reunite(SubHyperplane<S> other);
93 
94     /** Class holding the results of the {@link #split split} method.
95      * @param <U> Type of the embedding space.
96      */
97     class SplitSubHyperplane<U extends Space> {
98 
99         /** Part of the sub-hyperplane on the plus side of the splitting hyperplane. */
100         private final SubHyperplane<U> plus;
101 
102         /** Part of the sub-hyperplane on the minus side of the splitting hyperplane. */
103         private final SubHyperplane<U> minus;
104 
105         /** Build a SplitSubHyperplane from its parts.
106          * @param plus part of the sub-hyperplane on the plus side of the
107          * splitting hyperplane
108          * @param minus part of the sub-hyperplane on the minus side of the
109          * splitting hyperplane
110          */
SplitSubHyperplane(final SubHyperplane<U> plus, final SubHyperplane<U> minus)111         public SplitSubHyperplane(final SubHyperplane<U> plus,
112                                   final SubHyperplane<U> minus) {
113             this.plus  = plus;
114             this.minus = minus;
115         }
116 
117         /** Get the part of the sub-hyperplane on the plus side of the splitting hyperplane.
118          * @return part of the sub-hyperplane on the plus side of the splitting hyperplane
119          */
getPlus()120         public SubHyperplane<U> getPlus() {
121             return plus;
122         }
123 
124         /** Get the part of the sub-hyperplane on the minus side of the splitting hyperplane.
125          * @return part of the sub-hyperplane on the minus side of the splitting hyperplane
126          */
getMinus()127         public SubHyperplane<U> getMinus() {
128             return minus;
129         }
130 
131         /** Get the side of the split sub-hyperplane with respect to its splitter.
132          * @return {@link Side#PLUS} if only {@link #getPlus()} is neither null nor empty,
133          * {@link Side#MINUS} if only {@link #getMinus()} is neither null nor empty,
134          * {@link Side#BOTH} if both {@link #getPlus()} and {@link #getMinus()}
135          * are neither null nor empty or {@link Side#HYPER} if both {@link #getPlus()} and
136          * {@link #getMinus()} are either null or empty
137          * @since 3.6
138          */
getSide()139         public Side getSide() {
140             if (plus != null && !plus.isEmpty()) {
141                 if (minus != null && !minus.isEmpty()) {
142                     return Side.BOTH;
143                 } else {
144                     return Side.PLUS;
145                 }
146             } else if (minus != null && !minus.isEmpty()) {
147                 return Side.MINUS;
148             } else {
149                 return Side.HYPER;
150             }
151         }
152 
153     }
154 
155 }
156