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The Math project is a library of lightweight, self-contained mathematics and statistics components addressing the most common practical problems not immediately available in the Java programming language or commons-lang.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.math3.geometry.partitioning;
import org.apache.commons.math3.geometry.Space;
/** This class is a factory for {@link Region}.
* @param Type of the space.
* @version $Id: RegionFactory.java 1244107 2012-02-14 16:17:55Z erans $
* @since 3.0
*/
public class RegionFactory {
/** Visitor removing internal nodes attributes. */
private final NodesCleaner nodeCleaner;
/** Simple constructor.
*/
public RegionFactory() {
nodeCleaner = new NodesCleaner();
}
/** Build a convex region from a collection of bounding hyperplanes.
* @param hyperplanes collection of bounding hyperplanes
* @return a new convex region, or null if the collection is empty
*/
public Region buildConvex(final Hyperplane ... hyperplanes) {
if ((hyperplanes == null) || (hyperplanes.length == 0)) {
return null;
}
// use the first hyperplane to build the right class
final Region region = hyperplanes[0].wholeSpace();
// chop off parts of the space
BSPTree node = region.getTree(false);
node.setAttribute(Boolean.TRUE);
for (final Hyperplane hyperplane : hyperplanes) {
if (node.insertCut(hyperplane)) {
node.setAttribute(null);
node.getPlus().setAttribute(Boolean.FALSE);
node = node.getMinus();
node.setAttribute(Boolean.TRUE);
}
}
return region;
}
/** Compute the union of two regions.
* @param region1 first region (will be unusable after the operation as
* parts of it will be reused in the new region)
* @param region2 second region (will be unusable after the operation as
* parts of it will be reused in the new region)
* @return a new region, result of {@code region1 union region2}
*/
public Region union(final Region region1, final Region region2) {
final BSPTree tree =
region1.getTree(false).merge(region2.getTree(false), new UnionMerger());
tree.visit(nodeCleaner);
return region1.buildNew(tree);
}
/** Compute the intersection of two regions.
* @param region1 first region (will be unusable after the operation as
* parts of it will be reused in the new region)
* @param region2 second region (will be unusable after the operation as
* parts of it will be reused in the new region)
* @return a new region, result of {@code region1 intersection region2}
*/
public Region intersection(final Region region1, final Region region2) {
final BSPTree tree =
region1.getTree(false).merge(region2.getTree(false), new IntersectionMerger());
tree.visit(nodeCleaner);
return region1.buildNew(tree);
}
/** Compute the symmetric difference (exclusive or) of two regions.
* @param region1 first region (will be unusable after the operation as
* parts of it will be reused in the new region)
* @param region2 second region (will be unusable after the operation as
* parts of it will be reused in the new region)
* @return a new region, result of {@code region1 xor region2}
*/
public Region xor(final Region region1, final Region region2) {
final BSPTree tree =
region1.getTree(false).merge(region2.getTree(false), new XorMerger());
tree.visit(nodeCleaner);
return region1.buildNew(tree);
}
/** Compute the difference of two regions.
* @param region1 first region (will be unusable after the operation as
* parts of it will be reused in the new region)
* @param region2 second region (will be unusable after the operation as
* parts of it will be reused in the new region)
* @return a new region, result of {@code region1 minus region2}
*/
public Region difference(final Region region1, final Region region2) {
final BSPTree tree =
region1.getTree(false).merge(region2.getTree(false), new DifferenceMerger());
tree.visit(nodeCleaner);
return region1.buildNew(tree);
}
/** Get the complement of the region (exchanged interior/exterior).
* @param region region to complement, it will not modified, a new
* region independent region will be built
* @return a new region, complement of the specified one
*/
public Region getComplement(final Region region) {
return region.buildNew(recurseComplement(region.getTree(false)));
}
/** Recursively build the complement of a BSP tree.
* @param node current node of the original tree
* @return new tree, complement of the node
*/
private BSPTree recurseComplement(final BSPTree node) {
if (node.getCut() == null) {
return new BSPTree(((Boolean) node.getAttribute()) ? Boolean.FALSE : Boolean.TRUE);
}
@SuppressWarnings("unchecked")
BoundaryAttribute attribute = (BoundaryAttribute) node.getAttribute();
if (attribute != null) {
final SubHyperplane plusOutside =
(attribute.getPlusInside() == null) ? null : attribute.getPlusInside().copySelf();
final SubHyperplane plusInside =
(attribute.getPlusOutside() == null) ? null : attribute.getPlusOutside().copySelf();
attribute = new BoundaryAttribute(plusOutside, plusInside);
}
return new BSPTree(node.getCut().copySelf(),
recurseComplement(node.getPlus()),
recurseComplement(node.getMinus()),
attribute);
}
/** BSP tree leaf merger computing union of two regions. */
private class UnionMerger implements BSPTree.LeafMerger {
/** {@inheritDoc} */
public BSPTree merge(final BSPTree leaf, final BSPTree tree,
final BSPTree parentTree,
final boolean isPlusChild, final boolean leafFromInstance) {
if ((Boolean) leaf.getAttribute()) {
// the leaf node represents an inside cell
leaf.insertInTree(parentTree, isPlusChild);
return leaf;
}
// the leaf node represents an outside cell
tree.insertInTree(parentTree, isPlusChild);
return tree;
}
}
/** BSP tree leaf merger computing union of two regions. */
private class IntersectionMerger implements BSPTree.LeafMerger {
/** {@inheritDoc} */
public BSPTree merge(final BSPTree leaf, final BSPTree tree,
final BSPTree parentTree,
final boolean isPlusChild, final boolean leafFromInstance) {
if ((Boolean) leaf.getAttribute()) {
// the leaf node represents an inside cell
tree.insertInTree(parentTree, isPlusChild);
return tree;
}
// the leaf node represents an outside cell
leaf.insertInTree(parentTree, isPlusChild);
return leaf;
}
}
/** BSP tree leaf merger computing union of two regions. */
private class XorMerger implements BSPTree.LeafMerger {
/** {@inheritDoc} */
public BSPTree merge(final BSPTree leaf, final BSPTree tree,
final BSPTree parentTree, final boolean isPlusChild,
final boolean leafFromInstance) {
BSPTree t = tree;
if ((Boolean) leaf.getAttribute()) {
// the leaf node represents an inside cell
t = recurseComplement(t);
}
t.insertInTree(parentTree, isPlusChild);
return t;
}
}
/** BSP tree leaf merger computing union of two regions. */
private class DifferenceMerger implements BSPTree.LeafMerger {
/** {@inheritDoc} */
public BSPTree merge(final BSPTree leaf, final BSPTree tree,
final BSPTree parentTree, final boolean isPlusChild,
final boolean leafFromInstance) {
if ((Boolean) leaf.getAttribute()) {
// the leaf node represents an inside cell
final BSPTree argTree =
recurseComplement(leafFromInstance ? tree : leaf);
argTree.insertInTree(parentTree, isPlusChild);
return argTree;
}
// the leaf node represents an outside cell
final BSPTree instanceTree =
leafFromInstance ? leaf : tree;
instanceTree.insertInTree(parentTree, isPlusChild);
return instanceTree;
}
}
/** Visitor removing internal nodes attributes. */
private class NodesCleaner implements BSPTreeVisitor {
/** {@inheritDoc} */
public Order visitOrder(final BSPTree node) {
return Order.PLUS_SUB_MINUS;
}
/** {@inheritDoc} */
public void visitInternalNode(final BSPTree node) {
node.setAttribute(null);
}
/** {@inheritDoc} */
public void visitLeafNode(final BSPTree node) {
}
}
}