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 * https://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
18 /*
19 * This is not the original file distributed by the Apache Software Foundation
20 * It has been modified by the Hipparchus project
21 */
22 package org.hipparchus.geometry.partitioning;
23
24 import org.hipparchus.geometry.Space;
25
26 /** Visitor building boundary shell tree.
27 * <p>
28 * The boundary shell is represented as {@link BoundaryAttribute boundary attributes}
29 * at each internal node.
30 * </p>
31 * @param <S> Type of the space.
32 */
33 class BoundaryBuilder<S extends Space> implements BSPTreeVisitor<S> {
34
35 /** {@inheritDoc} */
36 @Override
37 public Order visitOrder(BSPTree<S> node) {
38 return Order.PLUS_MINUS_SUB;
39 }
40
41 /** {@inheritDoc} */
42 @Override
43 public void visitInternalNode(BSPTree<S> node) {
44
45 SubHyperplane<S> plusOutside = null;
46 SubHyperplane<S> plusInside = null;
47 NodesSet<S> splitters = null;
48
49 // characterize the cut sub-hyperplane,
50 // first with respect to the plus sub-tree
51 final Characterization<S> plusChar = new Characterization<>(node.getPlus(), node.getCut().copySelf());
52
53 if (plusChar.touchOutside()) {
54 // plusChar.outsideTouching() corresponds to a subset of the cut sub-hyperplane
55 // known to have outside cells on its plus side, we want to check if parts
56 // of this subset do have inside cells on their minus side
57 final Characterization<S> minusChar = new Characterization<>(node.getMinus(), plusChar.outsideTouching());
58 if (minusChar.touchInside()) {
59 // this part belongs to the boundary,
60 // it has the outside on its plus side and the inside on its minus side
61 plusOutside = minusChar.insideTouching();
62 splitters = new NodesSet<>();
63 splitters.addAll(minusChar.getInsideSplitters());
64 splitters.addAll(plusChar.getOutsideSplitters());
65 }
66 }
67
68 if (plusChar.touchInside()) {
69 // plusChar.insideTouching() corresponds to a subset of the cut sub-hyperplane
70 // known to have inside cells on its plus side, we want to check if parts
71 // of this subset do have outside cells on their minus side
72 final Characterization<S> minusChar = new Characterization<>(node.getMinus(), plusChar.insideTouching());
73 if (minusChar.touchOutside()) {
74 // this part belongs to the boundary,
75 // it has the inside on its plus side and the outside on its minus side
76 plusInside = minusChar.outsideTouching();
77 if (splitters == null) {
78 splitters = new NodesSet<>();
79 }
80 splitters.addAll(minusChar.getOutsideSplitters());
81 splitters.addAll(plusChar.getInsideSplitters());
82 }
83 }
84
85 if (splitters != null) {
86 // the parent nodes are natural splitters for boundary sub-hyperplanes
87 for (BSPTree<S> up = node.getParent(); up != null; up = up.getParent()) {
88 splitters.add(up);
89 }
90 }
91
92 // set the boundary attribute at non-leaf nodes
93 node.setAttribute(new BoundaryAttribute<>(plusOutside, plusInside, splitters));
94
95 }
96
97 /** {@inheritDoc} */
98 @Override
99 public void visitLeafNode(BSPTree<S> node) {
100 }
101
102 }