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Java example source code file (ConvexHullGenerator2DAbstractTest.java)

This example Java source code file (ConvexHullGenerator2DAbstractTest.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

arraylist, before, collection, convexhull2d, convexhullgenerator2d, convexhullgenerator2dabstracttest, location, mersennetwister, randomgenerator, region, test, util, vector2d

The ConvexHullGenerator2DAbstractTest.java Java example source code

/*
 * 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.euclidean.twod.hull;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

import org.apache.commons.math3.exception.NullArgumentException;
import org.apache.commons.math3.geometry.euclidean.twod.Euclidean2D;
import org.apache.commons.math3.geometry.euclidean.twod.Vector2D;
import org.apache.commons.math3.geometry.partitioning.Region;
import org.apache.commons.math3.geometry.partitioning.Region.Location;
import org.apache.commons.math3.random.MersenneTwister;
import org.apache.commons.math3.random.RandomGenerator;
import org.apache.commons.math3.util.FastMath;
import org.apache.commons.math3.util.MathArrays;
import org.apache.commons.math3.util.Precision;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;

/**
 * Abstract base test class for 2D convex hull generators.
 *
 */
public abstract class ConvexHullGenerator2DAbstractTest {

    protected ConvexHullGenerator2D generator;
    protected RandomGenerator random;

    protected abstract ConvexHullGenerator2D createConvexHullGenerator(boolean includeCollinearPoints);

    protected Collection<Vector2D> reducePoints(Collection points) {
        // do nothing by default, may be overridden by other tests
        return points;
    }

    @Before
    public void setUp() {
        // by default, do not include collinear points
        generator = createConvexHullGenerator(false);
        random = new MersenneTwister(10);
    }

    // ------------------------------------------------------------------------------

    @Test(expected = NullArgumentException.class)
    public void testNullArgument() {
        generator.generate(null);
    }

    @Test
    public void testEmpty() {
        ConvexHull2D hull = generator.generate(Collections.<Vector2D>emptyList());
        Assert.assertTrue(hull.getVertices().length == 0);
        Assert.assertTrue(hull.getLineSegments().length == 0);
    }

    @Test
    public void testOnePoint() {
        List<Vector2D> points = createRandomPoints(1);
        ConvexHull2D hull = generator.generate(points);
        Assert.assertTrue(hull.getVertices().length == 1);
        Assert.assertTrue(hull.getLineSegments().length == 0);
    }

    @Test
    public void testTwoPoints() {
        List<Vector2D> points = createRandomPoints(2);
        ConvexHull2D hull = generator.generate(points);
        Assert.assertTrue(hull.getVertices().length == 2);
        Assert.assertTrue(hull.getLineSegments().length == 1);
    }

    @Test
    public void testAllIdentical() {
        final Collection<Vector2D> points = new ArrayList();
        points.add(new Vector2D(1, 1));
        points.add(new Vector2D(1, 1));
        points.add(new Vector2D(1, 1));
        points.add(new Vector2D(1, 1));

        final ConvexHull2D hull = generator.generate(points);
        Assert.assertTrue(hull.getVertices().length == 1);
    }

    @Test
    public void testConvexHull() {
        // execute 100 random variations
        for (int i = 0; i < 100; i++) {
            // randomize the size from 4 to 100
            int size = (int) FastMath.floor(random.nextDouble() * 96.0 + 4.0);

            List<Vector2D> points = createRandomPoints(size);
            ConvexHull2D hull = generator.generate(reducePoints(points));
            checkConvexHull(points, hull);
        }
    }

    @Test
    public void testCollinearPoints() {
        final Collection<Vector2D> points = new ArrayList();
        points.add(new Vector2D(1, 1));
        points.add(new Vector2D(2, 2));
        points.add(new Vector2D(2, 4));
        points.add(new Vector2D(4, 1));
        points.add(new Vector2D(10, 1));

        final ConvexHull2D hull = generator.generate(points);
        checkConvexHull(points, hull);
    }

    @Test
    public void testCollinearPointsReverse() {
        final Collection<Vector2D> points = new ArrayList();
        points.add(new Vector2D(1, 1));
        points.add(new Vector2D(2, 2));
        points.add(new Vector2D(2, 4));
        points.add(new Vector2D(10, 1));
        points.add(new Vector2D(4, 1));

        final ConvexHull2D hull = generator.generate(points);
        checkConvexHull(points, hull);
    }

    @Test
    public void testCollinearPointsIncluded() {
        final Collection<Vector2D> points = new ArrayList();
        points.add(new Vector2D(1, 1));
        points.add(new Vector2D(2, 2));
        points.add(new Vector2D(2, 4));
        points.add(new Vector2D(4, 1));
        points.add(new Vector2D(10, 1));

        final ConvexHull2D hull = createConvexHullGenerator(true).generate(points);
        checkConvexHull(points, hull, true);
    }

    @Test
    public void testCollinearPointsIncludedReverse() {
        final Collection<Vector2D> points = new ArrayList();
        points.add(new Vector2D(1, 1));
        points.add(new Vector2D(2, 2));
        points.add(new Vector2D(2, 4));
        points.add(new Vector2D(10, 1));
        points.add(new Vector2D(4, 1));

        final ConvexHull2D hull = createConvexHullGenerator(true).generate(points);
        checkConvexHull(points, hull, true);
    }

    @Test
    public void testIdenticalPoints() {
        final Collection<Vector2D> points = new ArrayList();
        points.add(new Vector2D(1, 1));
        points.add(new Vector2D(2, 2));
        points.add(new Vector2D(2, 4));
        points.add(new Vector2D(4, 1));
        points.add(new Vector2D(1, 1));

        final ConvexHull2D hull = generator.generate(points);
        checkConvexHull(points, hull);
    }

    @Test
    public void testIdenticalPoints2() {
        final Collection<Vector2D> points = new ArrayList();
        points.add(new Vector2D(1, 1));
        points.add(new Vector2D(2, 2));
        points.add(new Vector2D(2, 4));
        points.add(new Vector2D(4, 1));
        points.add(new Vector2D(1, 1));

        final ConvexHull2D hull = createConvexHullGenerator(true).generate(points);
        checkConvexHull(points, hull, true);
    }

    @Test
    public void testClosePoints() {
        final Collection<Vector2D> points = new ArrayList();
        points.add(new Vector2D(1, 1));
        points.add(new Vector2D(2, 2));
        points.add(new Vector2D(2, 4));
        points.add(new Vector2D(4, 1));
        points.add(new Vector2D(1.00001, 1));

        final ConvexHull2D hull = generator.generate(points);
        checkConvexHull(points, hull);
    }

    @Test
    public void testCollinearPointOnExistingBoundary() {
        // MATH-1135: check that collinear points on the hull are handled correctly
        //            when only a minimal hull shall be constructed
        final Collection<Vector2D> points = new ArrayList();
        points.add(new Vector2D(7.3152, 34.7472));
        points.add(new Vector2D(6.400799999999997, 34.747199999999985));
        points.add(new Vector2D(5.486399999999997, 34.7472));
        points.add(new Vector2D(4.876799999999999, 34.7472));
        points.add(new Vector2D(4.876799999999999, 34.1376));
        points.add(new Vector2D(4.876799999999999, 30.48));
        points.add(new Vector2D(6.0959999999999965, 30.48));
        points.add(new Vector2D(6.0959999999999965, 34.1376));
        points.add(new Vector2D(7.315199999999996, 34.1376));
        points.add(new Vector2D(7.3152, 30.48));

        final ConvexHull2D hull = createConvexHullGenerator(false).generate(points);
        checkConvexHull(points, hull);
    }

    @Test
    public void testCollinearPointsInAnyOrder() {
        // MATH-1148: collinear points on the hull might be in any order
        //            make sure that they are processed in the proper order
        //            for each algorithm.

        List<Vector2D> points = new ArrayList();

        // first case: 3 points are collinear
        points.add(new Vector2D(16.078200000000184, -36.52519999989808));
        points.add(new Vector2D(19.164300000000186, -36.52519999989808));
        points.add(new Vector2D(19.1643, -25.28136477910407));
        points.add(new Vector2D(19.1643, -17.678400000004157));

        ConvexHull2D hull = createConvexHullGenerator(false).generate(points);
        checkConvexHull(points, hull);

        hull = createConvexHullGenerator(true).generate(points);
        checkConvexHull(points, hull, true);

        points.clear();

        // second case: multiple points are collinear
        points.add(new Vector2D(0, -29.959696875));
        points.add(new Vector2D(0, -31.621809375));
        points.add(new Vector2D(0, -28.435696875));
        points.add(new Vector2D(0, -33.145809375));
        points.add(new Vector2D(3.048, -33.145809375));
        points.add(new Vector2D(3.048, -31.621809375));
        points.add(new Vector2D(3.048, -29.959696875));
        points.add(new Vector2D(4.572, -33.145809375));
        points.add(new Vector2D(4.572, -28.435696875));

        hull = createConvexHullGenerator(false).generate(points);
        checkConvexHull(points, hull);

        hull = createConvexHullGenerator(true).generate(points);
        checkConvexHull(points, hull, true);
    }

    @Test
    public void testIssue1123() {

        List<Vector2D> points = new ArrayList();

        int[][] data = new int[][] { { -11, -1 }, { -11, 0 }, { -11, 1 },
                { -10, -3 }, { -10, -2 }, { -10, -1 }, { -10, 0 }, { -10, 1 },
                { -10, 2 }, { -10, 3 }, { -9, -4 }, { -9, -3 }, { -9, -2 },
                { -9, -1 }, { -9, 0 }, { -9, 1 }, { -9, 2 }, { -9, 3 },
                { -9, 4 }, { -8, -5 }, { -8, -4 }, { -8, -3 }, { -8, -2 },
                { -8, -1 }, { -8, 0 }, { -8, 1 }, { -8, 2 }, { -8, 3 },
                { -8, 4 }, { -8, 5 }, { -7, -6 }, { -7, -5 }, { -7, -4 },
                { -7, -3 }, { -7, -2 }, { -7, -1 }, { -7, 0 }, { -7, 1 },
                { -7, 2 }, { -7, 3 }, { -7, 4 }, { -7, 5 }, { -7, 6 },
                { -6, -7 }, { -6, -6 }, { -6, -5 }, { -6, -4 }, { -6, -3 },
                { -6, -2 }, { -6, -1 }, { -6, 0 }, { -6, 1 }, { -6, 2 },
                { -6, 3 }, { -6, 4 }, { -6, 5 }, { -6, 6 }, { -6, 7 },
                { -5, -7 }, { -5, -6 }, { -5, -5 }, { -5, -4 }, { -5, -3 },
                { -5, -2 }, { -5, 4 }, { -5, 5 }, { -5, 6 }, { -5, 7 },
                { -4, -7 }, { -4, -6 }, { -4, -5 }, { -4, -4 }, { -4, -3 },
                { -4, -2 }, { -4, 4 }, { -4, 5 }, { -4, 6 }, { -4, 7 },
                { -3, -8 }, { -3, -7 }, { -3, -6 }, { -3, -5 }, { -3, -4 },
                { -3, -3 }, { -3, -2 }, { -3, 4 }, { -3, 5 }, { -3, 6 },
                { -3, 7 }, { -3, 8 }, { -2, -8 }, { -2, -7 }, { -2, -6 },
                { -2, -5 }, { -2, -4 }, { -2, -3 }, { -2, -2 }, { -2, 4 },
                { -2, 5 }, { -2, 6 }, { -2, 7 }, { -2, 8 }, { -1, -8 },
                { -1, -7 }, { -1, -6 }, { -1, -5 }, { -1, -4 }, { -1, -3 },
                { -1, -2 }, { -1, 4 }, { -1, 5 }, { -1, 6 }, { -1, 7 },
                { -1, 8 }, { 0, -8 }, { 0, -7 }, { 0, -6 }, { 0, -5 },
                { 0, -4 }, { 0, -3 }, { 0, -2 }, { 0, 4 }, { 0, 5 }, { 0, 6 },
                { 0, 7 }, { 0, 8 }, { 1, -8 }, { 1, -7 }, { 1, -6 }, { 1, -5 },
                { 1, -4 }, { 1, -3 }, { 1, -2 }, { 1, -1 }, { 1, 0 }, { 1, 1 },
                { 1, 2 }, { 1, 3 }, { 1, 4 }, { 1, 5 }, { 1, 6 }, { 1, 7 },
                { 1, 8 }, { 2, -8 }, { 2, -7 }, { 2, -6 }, { 2, -5 },
                { 2, -4 }, { 2, -3 }, { 2, -2 }, { 2, -1 }, { 2, 0 }, { 2, 1 },
                { 2, 2 }, { 2, 3 }, { 2, 4 }, { 2, 5 }, { 2, 6 }, { 2, 7 },
                { 2, 8 }, { 3, -8 }, { 3, -7 }, { 3, -6 }, { 3, -5 },
                { 3, -4 }, { 3, -3 }, { 3, -2 }, { 3, -1 }, { 3, 0 }, { 3, 1 },
                { 3, 2 }, { 3, 3 }, { 3, 4 }, { 3, 5 }, { 3, 6 }, { 3, 7 },
                { 3, 8 }, { 4, -7 }, { 4, -6 }, { 4, -5 }, { 4, -4 },
                { 4, -3 }, { 4, -2 }, { 4, -1 }, { 4, 0 }, { 4, 1 }, { 4, 2 },
                { 4, 3 }, { 4, 4 }, { 4, 5 }, { 4, 6 }, { 4, 7 }, { 5, -7 },
                { 5, -6 }, { 5, -5 }, { 5, -4 }, { 5, -3 }, { 5, -2 },
                { 5, -1 }, { 5, 0 }, { 5, 1 }, { 5, 2 }, { 5, 3 }, { 5, 4 },
                { 5, 5 }, { 5, 6 }, { 5, 7 }, { 6, -7 }, { 6, -6 }, { 6, -5 },
                { 6, -4 }, { 6, -3 }, { 6, -2 }, { 6, -1 }, { 6, 0 }, { 6, 1 },
                { 6, 2 }, { 6, 3 }, { 6, 4 }, { 6, 5 }, { 6, 6 }, { 6, 7 },
                { 7, -6 }, { 7, -5 }, { 7, -4 }, { 7, -3 }, { 7, -2 },
                { 7, -1 }, { 7, 0 }, { 7, 1 }, { 7, 2 }, { 7, 3 }, { 7, 4 },
                { 7, 5 }, { 7, 6 }, { 8, -5 }, { 8, -4 }, { 8, -3 }, { 8, -2 },
                { 8, -1 }, { 8, 0 }, { 8, 1 }, { 8, 2 }, { 8, 3 }, { 8, 4 },
                { 8, 5 }, { 9, -4 }, { 9, -3 }, { 9, -2 }, { 9, -1 }, { 9, 0 },
                { 9, 1 }, { 9, 2 }, { 9, 3 }, { 9, 4 }, { 10, -3 }, { 10, -2 },
                { 10, -1 }, { 10, 0 }, { 10, 1 }, { 10, 2 }, { 10, 3 },
                { 11, -1 }, { 11, 0 }, { 11, 1 } };

        for (int[] line : data) {
            points.add(new Vector2D(line[0], line[1]));
        }

        Vector2D[] referenceHull = new Vector2D[] {
            new Vector2D(-11.0, -1.0),
            new Vector2D(-10.0, -3.0),
            new Vector2D( -6.0, -7.0),
            new Vector2D( -3.0, -8.0),
            new Vector2D(  3.0, -8.0),
            new Vector2D(  6.0, -7.0),
            new Vector2D( 10.0, -3.0),
            new Vector2D( 11.0, -1.0),
            new Vector2D( 11.0,  1.0),
            new Vector2D( 10.0,  3.0),
            new Vector2D(  6.0,  7.0),
            new Vector2D(  3.0,  8.0),
            new Vector2D( -3.0,  8.0),
            new Vector2D( -6.0,  7.0),
            new Vector2D(-10.0,  3.0),
            new Vector2D(-11.0,  1.0),
        };

        ConvexHull2D convHull = generator.generate(points);
        Region<Euclidean2D> hullRegion = convHull.createRegion();

        Assert.assertEquals(274.0, hullRegion.getSize(), 1.0e-12);
        double perimeter = 0;
        for (int i = 0; i < referenceHull.length; ++i) {
            perimeter += Vector2D.distance(referenceHull[i],
                                           referenceHull[(i + 1) % referenceHull.length]);
        }
        Assert.assertEquals(perimeter, hullRegion.getBoundarySize(), 1.0e-12);

        for (int i = 0; i < referenceHull.length; ++i) {
            Assert.assertEquals(Location.BOUNDARY, hullRegion.checkPoint(referenceHull[i]));
        }

    }

    // ------------------------------------------------------------------------------

    protected final List<Vector2D> createRandomPoints(int size) {
        // create the cloud container
        List<Vector2D> points = new ArrayList(size);
        // fill the cloud with a random distribution of points
        for (int i = 0; i < size; i++) {
            points.add(new Vector2D(random.nextDouble() * 2.0 - 1.0, random.nextDouble() * 2.0 - 1.0));
        }
        return points;
    }

    protected final void checkConvexHull(final Collection<Vector2D> points, final ConvexHull2D hull) {
        checkConvexHull(points, hull, false);
    }

    protected final void checkConvexHull(final Collection<Vector2D> points, final ConvexHull2D hull,
                                         final boolean includesCollinearPoints) {
        checkConvexHull(points, hull, includesCollinearPoints, 1e-10);
    }

    protected final void checkConvexHull(final Collection<Vector2D> points, final ConvexHull2D hull,
                                         final boolean includesCollinearPoints, final double tolerance) {
        Assert.assertNotNull(hull);
        Assert.assertTrue(isConvex(hull, includesCollinearPoints, tolerance));
        checkPointsInsideHullRegion(points, hull, includesCollinearPoints);
    }

    // verify that the constructed hull is really convex
    protected final boolean isConvex(final ConvexHull2D hull, final boolean includesCollinearPoints,
                                     final double tolerance) {

        final Vector2D[] points = hull.getVertices();
        int sign = 0;

        for (int i = 0; i < points.length; i++) {
            Vector2D p1 = points[i == 0 ? points.length - 1 : i - 1];
            Vector2D p2 = points[i];
            Vector2D p3 = points[i == points.length - 1 ? 0 : i + 1];

            Vector2D d1 = p2.subtract(p1);
            Vector2D d2 = p3.subtract(p2);

            Assert.assertTrue(d1.getNorm() > 1e-10);
            Assert.assertTrue(d2.getNorm() > 1e-10);

            final double cross = MathArrays.linearCombination(d1.getX(), d2.getY(), -d1.getY(), d2.getX());
            final int cmp = Precision.compareTo(cross, 0.0, tolerance);

            if (sign != 0 && cmp != sign) {
                if (includesCollinearPoints && cmp == 0) {
                    // in case of collinear points the cross product will be zero
                } else {
                    return false;
                }
            }

            sign = cmp;
        }

        return true;
    }

    // verify that all points are inside the convex hull region
    protected final void checkPointsInsideHullRegion(final Collection<Vector2D> points,
                                                     final ConvexHull2D hull,
                                                     final boolean includesCollinearPoints) {

        final Collection<Vector2D> hullVertices = Arrays.asList(hull.getVertices());
        final Region<Euclidean2D> region = hull.createRegion();

        for (final Vector2D p : points) {
            Location location = region.checkPoint(p);
            Assert.assertTrue(location != Location.OUTSIDE);

            if (location == Location.BOUNDARY && includesCollinearPoints) {
                Assert.assertTrue(hullVertices.contains(p));
            }
        }
    }
}

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