/*
    * 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
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  package org.apache.commons.geometry.euclidean.threed.shape;
  
  import java.io.IOException;
  import java.util.List;
  import java.util.function.DoubleSupplier;
  import java.util.regex.Pattern;
  import java.util.stream.Collectors;
  
  import org.apache.commons.geometry.core.GeometryTestUtils;
  import org.apache.commons.geometry.core.RegionLocation;
  import org.apache.commons.geometry.core.precision.DoublePrecisionContext;
  import org.apache.commons.geometry.core.precision.EpsilonDoublePrecisionContext;
  import org.apache.commons.geometry.euclidean.EuclideanTestUtils;
  import org.apache.commons.geometry.euclidean.threed.Bounds3D;
  import org.apache.commons.geometry.euclidean.threed.PlaneConvexSubset;
  import org.apache.commons.geometry.euclidean.threed.RegionBSPTree3D;
  import org.apache.commons.geometry.euclidean.threed.SphericalCoordinates;
  import org.apache.commons.geometry.euclidean.threed.Triangle3D;
  import org.apache.commons.geometry.euclidean.threed.Vector3D;
  import org.apache.commons.geometry.euclidean.threed.line.Line3D;
  import org.apache.commons.geometry.euclidean.threed.line.LineConvexSubset3D;
  import org.apache.commons.geometry.euclidean.threed.line.LinecastPoint3D;
  import org.apache.commons.geometry.euclidean.threed.line.Lines3D;
  import org.apache.commons.geometry.euclidean.threed.mesh.TriangleMesh;
  import org.apache.commons.numbers.angle.PlaneAngleRadians;
  import org.apache.commons.rng.UniformRandomProvider;
  import org.apache.commons.rng.simple.RandomSource;
  import org.junit.Assert;
  import org.junit.Test;
  
  public class SphereTest {
  
      private static final double TEST_EPS = 1e-10;
  
      private static final DoublePrecisionContext TEST_PRECISION =
              new EpsilonDoublePrecisionContext(TEST_EPS);
  
      @Test
      public void testFrom() {
          // arrange
          final Vector3D center = Vector3D.of(1, 2, 3);
  
          // act
          final Sphere s = Sphere.from(center, 3, TEST_PRECISION);
  
          // act/assert
          Assert.assertFalse(s.isFull());
          Assert.assertFalse(s.isEmpty());
  
          Assert.assertSame(center, s.getCenter());
          Assert.assertSame(center, s.getCentroid());
  
          Assert.assertEquals(3, s.getRadius(), 0.0);
  
          Assert.assertSame(TEST_PRECISION, s.getPrecision());
      }
  
      @Test
      public void testFrom_illegalCenter() {
          // act/assert
          GeometryTestUtils.assertThrows(
              () -> Sphere.from(Vector3D.of(Double.POSITIVE_INFINITY, 1, 2), 1, TEST_PRECISION),
              IllegalArgumentException.class);
          GeometryTestUtils.assertThrows(
              () -> Sphere.from(Vector3D.of(Double.NaN, 1, 2), 1, TEST_PRECISION),
              IllegalArgumentException.class);
      }
  
      @Test
      public void testFrom_illegalRadius() {
          // arrange
          final DoublePrecisionContext precision = new EpsilonDoublePrecisionContext(1e-2);
  
          // act/assert
          GeometryTestUtils.assertThrows(() -> Sphere.from(Vector3D.ZERO, -1, TEST_PRECISION),
                  IllegalArgumentException.class);
          GeometryTestUtils.assertThrows(() -> Sphere.from(Vector3D.ZERO, 0, TEST_PRECISION),
                  IllegalArgumentException.class);
          GeometryTestUtils.assertThrows(() -> Sphere.from(Vector3D.ZERO, Double.POSITIVE_INFINITY, TEST_PRECISION),
                  IllegalArgumentException.class);
          GeometryTestUtils.assertThrows(() -> Sphere.from(Vector3D.ZERO, Double.NaN, TEST_PRECISION),
                  IllegalArgumentException.class);
  
         GeometryTestUtils.assertThrows(() -> Sphere.from(Vector3D.ZERO, 1e-3, precision),
                 IllegalArgumentException.class);
     }
 
     @Test
     public void testGeometricProperties() {
         // arrange
         final double r = 2;
         final Sphere s = Sphere.from(Vector3D.of(1, 2, 3), r, TEST_PRECISION);
 
         // act/assert
         Assert.assertEquals(4 * Math.PI * r * r, s.getBoundarySize(), TEST_EPS);
         Assert.assertEquals((4.0 * Math.PI * r * r * r) / 3.0, s.getSize(), TEST_EPS);
     }
 
     @Test
     public void testClassify() {
         // arrange
         final Vector3D center = Vector3D.of(1, 2, 3);
         final double radius = 4;
         final Sphere s = Sphere.from(center, radius, TEST_PRECISION);
 
         EuclideanTestUtils.permute(0, PlaneAngleRadians.TWO_PI, 0.2, (azimuth, polar) -> {
             // act/assert
             EuclideanTestUtils.assertRegionLocation(s, RegionLocation.OUTSIDE,
                     SphericalCoordinates.of(radius + 1, azimuth, polar)
                         .toVector()
                         .add(center));
 
             EuclideanTestUtils.assertRegionLocation(s, RegionLocation.BOUNDARY,
                     SphericalCoordinates.of(radius + 1e-12, azimuth, polar)
                         .toVector()
                         .add(center));
 
             EuclideanTestUtils.assertRegionLocation(s, RegionLocation.INSIDE,
                     SphericalCoordinates.of(radius - 1, azimuth, polar)
                         .toVector()
                         .add(center));
         });
     }
 
     @Test
     public void testContains() {
      // arrange
         final Vector3D center = Vector3D.of(1, 2, 3);
         final double radius = 4;
         final Sphere s = Sphere.from(center, radius, TEST_PRECISION);
 
         EuclideanTestUtils.permute(0, PlaneAngleRadians.TWO_PI, 0.2, (azimuth, polar) -> {
             // act/assert
             checkContains(s, false,
                     SphericalCoordinates.of(radius + 1, azimuth, polar)
                         .toVector()
                         .add(center));
 
             checkContains(s, true,
                     SphericalCoordinates.of(radius - 1, azimuth, polar)
                         .toVector()
                         .add(center),
                     SphericalCoordinates.of(radius + 1e-12, azimuth, polar)
                         .toVector()
                         .add(center));
         });
     }
 
     @Test
     public void testProject() {
         // arrange
         final Vector3D center = Vector3D.of(1.5, 2.5, 3.5);
         final double radius = 3;
         final Sphere s = Sphere.from(center, radius, TEST_PRECISION);
 
         EuclideanTestUtils.permute(-4, 4, 1, (x, y, z) -> {
             final Vector3D pt = Vector3D.of(x, y, z);
 
             // act
             final Vector3D projection = s.project(pt);
 
             // assert
             Assert.assertEquals(radius, center.distance(projection), TEST_EPS);
             EuclideanTestUtils.assertCoordinatesEqual(center.directionTo(pt),
                     center.directionTo(projection), TEST_EPS);
         });
     }
 
     @Test
     public void testProject_argumentEqualsCenter() {
         // arrange
         final Sphere c = Sphere.from(Vector3D.of(1, 2, 3), 2, TEST_PRECISION);
 
         // act
         final Vector3D projection = c.project(Vector3D.of(1, 2, 3));
 
         // assert
         EuclideanTestUtils.assertCoordinatesEqual(Vector3D.of(3, 2, 3), projection, TEST_EPS);
     }
 
     @Test
     public void testIntersections() {
         // --- arrange
         final Sphere s = Sphere.from(Vector3D.of(2, 1, 3), 2, TEST_PRECISION);
         final double sqrt3 = Math.sqrt(3);
 
         // --- act/assert
         // descending along y in x-y plane
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(-1, 4, 3), Vector3D.of(5, 4, 3), TEST_PRECISION));
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(-1, 3, 3), Vector3D.of(5, 3, 3), TEST_PRECISION),
                 Vector3D.of(2, 3, 3));
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(-1, 2, 3), Vector3D.of(5, 2, 3), TEST_PRECISION),
                 Vector3D.of(2 - sqrt3, 2, 3), Vector3D.of(2 + sqrt3, 2, 3));
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(-1, 1, 3), Vector3D.of(5, 1, 3), TEST_PRECISION),
                 Vector3D.of(0, 1, 3), Vector3D.of(4, 1, 3));
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(-1, 0, 3), Vector3D.of(5, 0, 3), TEST_PRECISION),
                 Vector3D.of(2 - sqrt3, 0, 3), Vector3D.of(2 + sqrt3, 0, 3));
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(-1, -1, 3), Vector3D.of(5, -1, 3), TEST_PRECISION),
                 Vector3D.of(2, -1, 3));
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(-1, -2, 3), Vector3D.of(5, -2, 3), TEST_PRECISION));
 
         // ascending along x in x-y plane
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(-1, -2, 3), Vector3D.of(-1, 5, 3), TEST_PRECISION));
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(0, -2, 3), Vector3D.of(0, 5, 3), TEST_PRECISION),
                 Vector3D.of(0, 1, 3));
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(1, -2, 3), Vector3D.of(1, 5, 3), TEST_PRECISION),
                 Vector3D.of(1, 1 - sqrt3, 3), Vector3D.of(1, 1 + sqrt3, 3));
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(2, -2, 3), Vector3D.of(2, 5, 3), TEST_PRECISION),
                 Vector3D.of(2, -1, 3), Vector3D.of(2, 3, 3));
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(3, -2, 3), Vector3D.of(3, 5, 3), TEST_PRECISION),
                 Vector3D.of(3, 1 - sqrt3, 3), Vector3D.of(3, 1 + sqrt3, 3));
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(4, -2, 3), Vector3D.of(4, 5, 3), TEST_PRECISION),
                 Vector3D.of(4, 1, 3));
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(5, -2, 3), Vector3D.of(5, 5, 3), TEST_PRECISION));
 
         // descending along z in y-z plane
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(2, -2, 6), Vector3D.of(2, 4, 6), TEST_PRECISION));
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(2, -2, 5), Vector3D.of(2, 4, 5), TEST_PRECISION),
                 Vector3D.of(2, 1, 5));
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(2, -2, 4), Vector3D.of(2, 4, 4), TEST_PRECISION),
                 Vector3D.of(2, 1 - sqrt3, 4), Vector3D.of(2, 1 + sqrt3, 4));
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(2, -2, 3), Vector3D.of(2, 4, 3), TEST_PRECISION),
                 Vector3D.of(2, -1, 3), Vector3D.of(2, 3, 3));
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(2, -2, 2), Vector3D.of(2, 4, 2), TEST_PRECISION),
                 Vector3D.of(2, 1 - sqrt3, 2), Vector3D.of(2, 1 + sqrt3, 2));
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(2, -2, 1), Vector3D.of(2, 4, 1), TEST_PRECISION),
                 Vector3D.of(2, 1, 1));
         checkIntersections(s, Lines3D.fromPoints(Vector3D.of(2, -2, 0), Vector3D.of(2, 4, 0), TEST_PRECISION));
 
         // diagonal from origin
         final Vector3D center = s.getCenter();
         checkIntersections(s, Lines3D.fromPoints(Vector3D.ZERO, s.getCenter(), TEST_PRECISION),
                 center.withNorm(center.norm() - s.getRadius()), center.withNorm(center.norm() + s.getRadius()));
     }
 
     @Test
     public void testLinecast() {
         // arrange
         final Sphere s = Sphere.from(Vector3D.of(2, 1, 3), 2, TEST_PRECISION);
         final double sqrt3 = Math.sqrt(3);
 
         // act/assert
         checkLinecast(s, Lines3D.segmentFromPoints(Vector3D.of(-1, 0, 3), Vector3D.of(5, 0, 3), TEST_PRECISION),
                 Vector3D.of(2 - sqrt3, 0, 3), Vector3D.of(2 + sqrt3, 0, 3));
         checkLinecast(s, Lines3D.segmentFromPoints(Vector3D.of(-1, 3, 3), Vector3D.of(5, 3, 3), TEST_PRECISION),
                 Vector3D.of(2, 3, 3));
         checkLinecast(s, Lines3D.segmentFromPoints(Vector3D.of(-1, -2, 3), Vector3D.of(5, -2, 3), TEST_PRECISION));
     }
 
     @Test
     public void testLinecast_intersectionsNotInSegment() {
         // arrange
         final Sphere s = Sphere.from(Vector3D.of(2, 1, 3), 2, TEST_PRECISION);
         final Line3D line = Lines3D.fromPointAndDirection(Vector3D.of(0, 0, 3), Vector3D.Unit.PLUS_X, TEST_PRECISION);
 
         // act/assert
         checkLinecast(s, line.segment(-1, 0));
         checkLinecast(s, line.segment(1.5, 2.5));
         checkLinecast(s, line.segment(1.5, 2.5));
         checkLinecast(s, line.segment(4, 5));
     }
 
     @Test
     public void testLinecast_segmentPointOnBoundary() {
         // arrange
         final Sphere s = Sphere.from(Vector3D.of(2, 1, 3), 2, TEST_PRECISION);
         final Line3D line = Lines3D.fromPointAndDirection(Vector3D.of(0, 0, 3), Vector3D.Unit.PLUS_X, TEST_PRECISION);
         final double sqrt3 = Math.sqrt(3);
         final double start = 2 - sqrt3;
         final double end = 2 + sqrt3;
 
         // act/assert
         checkLinecast(s, line.segment(start, 2), Vector3D.of(start, 0, 3));
         checkLinecast(s, line.segment(start, end), Vector3D.of(start, 0, 3), Vector3D.of(end, 0, 3));
         checkLinecast(s, line.segment(end, 5), Vector3D.of(end, 0, 3));
     }
 
     @Test
     public void testToTree_zeroSubdivisions() throws IOException {
         // arrange
         final double r = 2;
         final Sphere s = Sphere.from(Vector3D.of(2, 1, 3), r, TEST_PRECISION);
 
         // act
         final RegionBSPTree3D tree = s.toTree(0);
 
         // assert
         checkBasicApproximationProperties(s, tree);
 
         final List<PlaneConvexSubset> boundaries = tree.getBoundaries();
         Assert.assertEquals(8, boundaries.size());
 
         final List<Triangle3D> triangles = tree.triangleStream().collect(Collectors.toList());
         Assert.assertEquals(8, triangles.size());
 
         final double expectedSize = (4.0 / 3.0) * r * r * r;
         Assert.assertEquals(expectedSize, tree.getSize(), TEST_EPS);
     }
 
     @Test
     public void testToTree_oneSubdivision() throws IOException {
         // arrange
         final double r = 2;
         final Sphere s = Sphere.from(Vector3D.of(2, 1, 3), r, TEST_PRECISION);
 
         // act
         final RegionBSPTree3D tree = s.toTree(1);
 
         // assert
         checkBasicApproximationProperties(s, tree);
 
         final List<PlaneConvexSubset> boundaries = tree.getBoundaries();
         Assert.assertEquals(32, boundaries.size());
 
         final List<Triangle3D> triangles = tree.triangleStream().collect(Collectors.toList());
         Assert.assertEquals(32, triangles.size());
 
         Assert.assertTrue(tree.getSize() <= s.getSize());
     }
 
     @Test
     public void testToTree_multipleSubdivisionCounts() throws Exception {
         // -- arrange
         final Sphere s = Sphere.from(Vector3D.of(-3, 5, 1), 10, TEST_PRECISION);
 
         final int min = 0;
         final int max = 5;
 
         RegionBSPTree3D tree;
 
         double sizeDiff;
         double prevSizeDiff = Double.POSITIVE_INFINITY;
 
         for (int n = min; n <= max; ++n) {
             // -- act
             tree = s.toTree(n);
 
             // -- assert
             checkBasicApproximationProperties(s, tree);
 
             final int expectedTriangles = (int) (8 * Math.pow(4, n));
             final List<PlaneConvexSubset> boundaries = tree.getBoundaries();
             Assert.assertEquals(expectedTriangles, boundaries.size());
 
             final List<Triangle3D> triangles = tree.triangleStream().collect(Collectors.toList());
             Assert.assertEquals(expectedTriangles, triangles.size());
 
             // check that we get closer and closer to the correct size as we add more segments
             sizeDiff = s.getSize() - tree.getSize();
             Assert.assertTrue("Expected size difference to decrease: n= " +
                     n + ", prevSizeDiff= " + prevSizeDiff + ", sizeDiff= " + sizeDiff, sizeDiff < prevSizeDiff);
 
             prevSizeDiff = sizeDiff;
         }
     }
 
     @Test
     public void testToTree_randomSpheres() {
         // arrange
         final UniformRandomProvider rand = RandomSource.create(RandomSource.XO_RO_SHI_RO_128_PP, 1L);
         final DoublePrecisionContext precision = new EpsilonDoublePrecisionContext(1e-10);
         final double min = 1e-1;
         final double max = 1e2;
 
         final DoubleSupplier randDouble = () -> (rand.nextDouble() * (max - min)) + min;
 
         final int count = 10;
         for (int i = 0; i < count; ++i) {
             final Vector3D center = Vector3D.of(
                     randDouble.getAsDouble(),
                     randDouble.getAsDouble(),
                     randDouble.getAsDouble());
 
             final double radius = randDouble.getAsDouble();
             final Sphere sphere = Sphere.from(center, radius, precision);
 
             for (int s = 0; s < 7; ++s) {
                 // act
                 final RegionBSPTree3D tree = sphere.toTree(s);
 
                 // assert
                 Assert.assertEquals((int)(8 * Math.pow(4, s)), tree.getBoundaries().size());
                 Assert.assertTrue(tree.isFinite());
                 Assert.assertFalse(tree.isEmpty());
                 Assert.assertTrue(tree.getSize() < sphere.getSize());
             }
         }
     }
 
     @Test
     public void testToTree_closeApproximation() throws IOException {
         // arrange
         final Sphere s = Sphere.from(Vector3D.ZERO, 1, TEST_PRECISION);
 
         // act
         final RegionBSPTree3D tree = s.toTree(8);
 
         // assert
         checkBasicApproximationProperties(s, tree);
 
         final double eps = 1e-3;
         Assert.assertTrue(tree.isFinite());
         Assert.assertEquals(s.getSize(), tree.getSize(), eps);
         Assert.assertEquals(s.getBoundarySize(), tree.getBoundarySize(), eps);
         EuclideanTestUtils.assertCoordinatesEqual(s.getCentroid(), tree.getCentroid(), eps);
     }
 
     @Test
     public void testToTree_subdivideFails() {
         // arrange
         final DoublePrecisionContext precision = new EpsilonDoublePrecisionContext(1e-5);
         final Sphere s = Sphere.from(Vector3D.ZERO, 1, precision);
 
         // act/assert
         GeometryTestUtils.assertThrows(() -> {
             s.toTree(6);
         }, IllegalStateException.class,
                 Pattern.compile("^Failed to construct sphere approximation with subdivision count 6:.*"));
     }
 
     @Test
     public void testToTree_invalidArgs() {
         // arrange
         final Sphere s = Sphere.from(Vector3D.of(2, 1, 3), 2, TEST_PRECISION);
 
         // act/assert
         GeometryTestUtils.assertThrows(() -> {
             s.toTree(-1);
         }, IllegalArgumentException.class,
                 "Number of sphere approximation subdivisions must be greater than or equal to zero; was -1");
     }
 
     @Test
     public void testToMesh_zeroSubdivisions() {
         // arrange
         final Sphere s = Sphere.from(Vector3D.of(1, 2, 3), 2, TEST_PRECISION);
 
         // act
         final TriangleMesh mesh = s.toTriangleMesh(0);
 
         // assert
         Assert.assertEquals(6, mesh.getVertexCount());
         Assert.assertEquals(8, mesh.getFaceCount());
 
         final Bounds3D bounds = mesh.getBounds();
         EuclideanTestUtils.assertCoordinatesEqual(Vector3D.of(-1, 0, 1), bounds.getMin(), TEST_EPS);
         EuclideanTestUtils.assertCoordinatesEqual(Vector3D.of(3, 4, 5), bounds.getMax(), TEST_EPS);
 
         Assert.assertTrue(mesh.toTree().isFinite());
     }
 
     @Test
     public void testToMesh_manySubdivisions() {
         // arrange
         final Sphere s = Sphere.from(Vector3D.of(1, 2, 3), 2, TEST_PRECISION);
         final int subdivisions = 5;
 
         // act
         final TriangleMesh mesh = s.toTriangleMesh(subdivisions);
 
         // assert
         Assert.assertEquals((int) (8 * Math.pow(4, subdivisions)), mesh.getFaceCount());
 
         final Bounds3D bounds = mesh.getBounds();
         EuclideanTestUtils.assertCoordinatesEqual(Vector3D.of(-1, 0, 1), bounds.getMin(), TEST_EPS);
         EuclideanTestUtils.assertCoordinatesEqual(Vector3D.of(3, 4, 5), bounds.getMax(), TEST_EPS);
 
         final RegionBSPTree3D tree = RegionBSPTree3D.partitionedRegionBuilder()
                 .insertAxisAlignedGrid(bounds, 3, TEST_PRECISION)
                 .insertBoundaries(mesh)
                 .build();
 
         Assert.assertTrue(tree.isFinite());
 
         final double approximationEps = 0.1;
         Assert.assertEquals(s.getSize(), tree.getSize(), approximationEps);
         Assert.assertEquals(s.getBoundarySize(), tree.getBoundarySize(), approximationEps);
 
         EuclideanTestUtils.assertCoordinatesEqual(s.getCentroid(), tree.getCentroid(), TEST_EPS);
     }
 
     @Test
     public void testToMesh_invalidArgs() {
         // arrange
         final Sphere s = Sphere.from(Vector3D.of(2, 1, 3), 2, TEST_PRECISION);
 
         // act/assert
         GeometryTestUtils.assertThrows(() -> {
             s.toTriangleMesh(-1);
         }, IllegalArgumentException.class,
                 "Number of sphere approximation subdivisions must be greater than or equal to zero; was -1");
     }
 
     @Test
     public void testHashCode() {
         // arrange
         final DoublePrecisionContext otherPrecision = new EpsilonDoublePrecisionContext(1e-2);
 
         final Sphere a = Sphere.from(Vector3D.of(1, 2, 3), 3, TEST_PRECISION);
         final Sphere b = Sphere.from(Vector3D.of(1, 1, 3), 3, TEST_PRECISION);
         final Sphere c = Sphere.from(Vector3D.of(1, 2, 3), 4, TEST_PRECISION);
         final Sphere d = Sphere.from(Vector3D.of(1, 2, 3), 3, otherPrecision);
         final Sphere e = Sphere.from(Vector3D.of(1, 2, 3), 3, TEST_PRECISION);
 
         // act
         final int hash = a.hashCode();
 
         // act/assert
         Assert.assertEquals(hash, a.hashCode());
 
         Assert.assertNotEquals(hash, b.hashCode());
         Assert.assertNotEquals(hash, c.hashCode());
         Assert.assertNotEquals(hash, d.hashCode());
 
         Assert.assertEquals(hash, e.hashCode());
     }
 
     @Test
     public void testEquals() {
         // arrange
         final DoublePrecisionContext precision = new EpsilonDoublePrecisionContext(1e-2);
 
         final Sphere a = Sphere.from(Vector3D.of(1, 2, 3), 3, TEST_PRECISION);
         final Sphere b = Sphere.from(Vector3D.of(1, 1, 3), 3, TEST_PRECISION);
         final Sphere c = Sphere.from(Vector3D.of(1, 2, 3), 4, TEST_PRECISION);
         final Sphere d = Sphere.from(Vector3D.of(1, 2, 3), 3, precision);
         final Sphere e = Sphere.from(Vector3D.of(1, 2, 3), 3, TEST_PRECISION);
 
         // act/assert
         Assert.assertEquals(a, a);
 
         Assert.assertFalse(a.equals(null));
         Assert.assertFalse(a.equals(new Object()));
 
         Assert.assertNotEquals(a, b);
         Assert.assertNotEquals(a, c);
         Assert.assertNotEquals(a, d);
 
         Assert.assertEquals(a, e);
     }
 
     @Test
     public void testToString() {
         // arrange
         final Sphere c = Sphere.from(Vector3D.of(1, 2, 3), 3, TEST_PRECISION);
 
         // act
         final String str = c.toString();
 
         // assert
         Assert.assertEquals("Sphere[center= (1.0, 2.0, 3.0), radius= 3.0]", str);
     }
 
     private static void checkContains(final Sphere sphere, final boolean contains, final Vector3D... pts) {
         for (final Vector3D pt : pts) {
             Assert.assertEquals("Expected circle to " + (contains ? "" : "not") + "contain point " + pt,
                     contains, sphere.contains(pt));
         }
     }
 
     private static void checkIntersections(final Sphere sphere, final Line3D line, final Vector3D... expectedPts) {
         // --- act
         // compute the intersections forward and reverse
         final List<Vector3D> actualPtsForward = sphere.intersections(line);
         final List<Vector3D> actualPtsReverse = sphere.intersections(line.reverse());
 
         final Vector3D actualFirstForward = sphere.firstIntersection(line);
         final Vector3D actualFirstReverse = sphere.firstIntersection(line.reverse());
 
         // --- assert
         final int len = expectedPts.length;
 
         // check the lists
         Assert.assertEquals(len, actualPtsForward.size());
         Assert.assertEquals(len, actualPtsReverse.size());
 
         for (int i = 0; i < len; ++i) {
             EuclideanTestUtils.assertCoordinatesEqual(expectedPts[i], actualPtsForward.get(i), TEST_EPS);
             Assert.assertEquals(sphere.getRadius(), sphere.getCenter().distance(actualPtsForward.get(i)), TEST_EPS);
 
             EuclideanTestUtils.assertCoordinatesEqual(expectedPts[len - i - 1], actualPtsReverse.get(i), TEST_EPS);
             Assert.assertEquals(sphere.getRadius(), sphere.getCenter().distance(actualPtsReverse.get(i)), TEST_EPS);
         }
 
         // check the single intersection points
         if (len > 0) {
             Assert.assertNotNull(actualFirstForward);
             Assert.assertNotNull(actualFirstReverse);
 
             EuclideanTestUtils.assertCoordinatesEqual(expectedPts[0], actualFirstForward, TEST_EPS);
             EuclideanTestUtils.assertCoordinatesEqual(expectedPts[len - 1], actualFirstReverse, TEST_EPS);
         } else {
             Assert.assertNull(actualFirstForward);
             Assert.assertNull(actualFirstReverse);
         }
     }
 
     private static void checkLinecast(final Sphere s, final LineConvexSubset3D segment, final Vector3D... expectedPts) {
         // check linecast
         final List<LinecastPoint3D> results = s.linecast(segment);
         Assert.assertEquals(expectedPts.length, results.size());
 
         LinecastPoint3D actual;
         Vector3D expected;
         for (int i = 0; i < expectedPts.length; ++i) {
             expected = expectedPts[i];
             actual = results.get(i);
 
             EuclideanTestUtils.assertCoordinatesEqual(expected, actual.getPoint(), TEST_EPS);
             EuclideanTestUtils.assertCoordinatesEqual(s.getCenter().directionTo(expected), actual.getNormal(), TEST_EPS);
             Assert.assertSame(segment.getLine(), actual.getLine());
         }
 
         // check linecastFirst
         final LinecastPoint3D firstResult = s.linecastFirst(segment);
         if (expectedPts.length > 0) {
             Assert.assertEquals(results.get(0), firstResult);
         } else {
             Assert.assertNull(firstResult);
         }
     }
 
     /**
      * Check a number of standard properties for bsp trees generated as sphere approximations.
      */
     private static void checkBasicApproximationProperties(final Sphere s, final RegionBSPTree3D tree) {
         Assert.assertFalse(tree.isFull());
         Assert.assertFalse(tree.isEmpty());
         Assert.assertTrue(tree.isFinite());
         Assert.assertFalse(tree.isInfinite());
 
         // volume must be less than the sphere
         Assert.assertTrue("Expected approximation volume to be less than circle", tree.getSize() < s.getSize());
 
         // all vertices must be inside the sphere or on the boundary
         for (final PlaneConvexSubset boundary : tree.getBoundaries()) {
             Assert.assertTrue(boundary.isFinite());
 
             for (final Vector3D vertex : boundary.getVertices()) {
                 Assert.assertTrue("Expected vertex to be contained in sphere: " + vertex, s.contains(vertex));
             }
         }
 
         // sphere must contain centroid
         EuclideanTestUtils.assertRegionLocation(s, RegionLocation.INSIDE, tree.getCentroid());
     }
 }