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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.geometry.euclidean.internal;
18  
19  import java.util.ArrayList;
20  import java.util.Arrays;
21  import java.util.Collections;
22  import java.util.List;
23  import java.util.function.Function;
24  
25  import org.apache.commons.geometry.core.GeometryTestUtils;
26  import org.apache.commons.geometry.euclidean.EuclideanTestUtils;
27  import org.apache.commons.geometry.euclidean.threed.Vector3D;
28  import org.apache.commons.numbers.core.Precision;
29  import org.junit.jupiter.api.Assertions;
30  import org.junit.jupiter.api.Test;
31  
32  class EuclideanUtilsTest {
33  
34      private static final double TEST_EPS = 1e-10;
35  
36      private static final Precision.DoubleEquivalence TEST_PRECISION =
37              Precision.doubleEquivalenceOfEpsilon(TEST_EPS);
38  
39      @Test
40      void testConvexPolygonToTriangleFan_threeVertices() {
41          // arrange
42          final Vector3D p1 = Vector3D.ZERO;
43          final Vector3D p2 = Vector3D.of(1, 0, 0);
44          final Vector3D p3 = Vector3D.of(0, 1, 0);
45  
46          final List<List<Vector3D>> tris = new ArrayList<>();
47  
48          // act
49          EuclideanUtils.convexPolygonToTriangleFan(Arrays.asList(p1, p2, p3), tris::add);
50  
51          // assert
52          Assertions.assertEquals(1, tris.size());
53          EuclideanTestUtils.assertVertexLoopSequence(Arrays.asList(p1, p2, p3), tris.get(0), TEST_PRECISION);
54      }
55  
56      @Test
57      void testConvexPolygonToTriangleFan_fourVertices() {
58          // arrange
59          final Vector3D p1 = Vector3D.ZERO;
60          final Vector3D p2 = Vector3D.of(1, 0, 0);
61          final Vector3D p3 = Vector3D.of(1, 1, 0);
62          final Vector3D p4 = Vector3D.of(0, 1, 0);
63  
64          final List<List<Vector3D>> tris = new ArrayList<>();
65  
66          // act
67          EuclideanUtils.convexPolygonToTriangleFan(Arrays.asList(p1, p2, p3, p4), tris::add);
68  
69          // assert
70          Assertions.assertEquals(2, tris.size());
71  
72          EuclideanTestUtils.assertVertexLoopSequence(Arrays.asList(p1, p2, p3), tris.get(0), TEST_PRECISION);
73          EuclideanTestUtils.assertVertexLoopSequence(Arrays.asList(p1, p3, p4), tris.get(1), TEST_PRECISION);
74      }
75  
76      @Test
77      void testConvexPolygonToTriangleFan_fourVertices_chooseLargestInteriorAngleForBase() {
78          // arrange
79          final Vector3D p1 = Vector3D.ZERO;
80          final Vector3D p2 = Vector3D.of(1, 0, 0);
81          final Vector3D p3 = Vector3D.of(2, 1, 0);
82          final Vector3D p4 = Vector3D.of(1.5, 1, 0);
83  
84          final List<List<Vector3D>> tris = new ArrayList<>();
85  
86          // act
87          EuclideanUtils.convexPolygonToTriangleFan(Arrays.asList(p1, p2, p3, p4), tris::add);
88  
89          // assert
90          Assertions.assertEquals(2, tris.size());
91          EuclideanTestUtils.assertVertexLoopSequence(Arrays.asList(p4, p1, p2), tris.get(0), TEST_PRECISION);
92          EuclideanTestUtils.assertVertexLoopSequence(Arrays.asList(p4, p2, p3), tris.get(1), TEST_PRECISION);
93      }
94  
95      @Test
96      void testConvexPolygonToTriangleFan_fourVertices_distancesLessThanPrecision() {
97          // This test checks that the triangle fan algorithm is not affected by the distances between
98          // the vertices, just as long as the points are not exactly equal. Callers are responsible for
99          // ensuring that the points are actually distinct according to the relevant precision context.
100 
101         // arrange
102         final Vector3D p1 = Vector3D.ZERO;
103         final Vector3D p2 = Vector3D.of(1e-20, 0, 0);
104         final Vector3D p3 = Vector3D.of(1e-20, 1e-20, 0);
105         final Vector3D p4 = Vector3D.of(0, 1e-20, 0);
106 
107         final List<List<Vector3D>> tris = new ArrayList<>();
108 
109         // act
110         EuclideanUtils.convexPolygonToTriangleFan(Arrays.asList(p1, p2, p3, p4), tris::add);
111 
112         // assert
113         Assertions.assertEquals(2, tris.size());
114         EuclideanTestUtils.assertVertexLoopSequence(Arrays.asList(p1, p2, p3), tris.get(0), TEST_PRECISION);
115         EuclideanTestUtils.assertVertexLoopSequence(Arrays.asList(p1, p3, p4), tris.get(1), TEST_PRECISION);
116     }
117 
118     @Test
119     void testConvexPolygonToTriangleFan_sixVertices() {
120         // arrange
121         final Vector3D p1 = Vector3D.ZERO;
122         final Vector3D p2 = Vector3D.of(1, -1, 0);
123         final Vector3D p3 = Vector3D.of(1.5, -1, 0);
124         final Vector3D p4 = Vector3D.of(5, 0, 0);
125         final Vector3D p5 = Vector3D.of(3, 1, 0);
126         final Vector3D p6 = Vector3D.of(0.5, 1, 0);
127 
128         final List<List<Vector3D>> tris = new ArrayList<>();
129 
130         // act
131         EuclideanUtils.convexPolygonToTriangleFan(Arrays.asList(p1, p2, p3, p4, p5, p6), tris::add);
132 
133         // assert
134         Assertions.assertEquals(4, tris.size());
135         EuclideanTestUtils.assertVertexLoopSequence(Arrays.asList(p3, p4, p5), tris.get(0), TEST_PRECISION);
136         EuclideanTestUtils.assertVertexLoopSequence(Arrays.asList(p3, p5, p6), tris.get(1), TEST_PRECISION);
137         EuclideanTestUtils.assertVertexLoopSequence(Arrays.asList(p3, p6, p1), tris.get(2), TEST_PRECISION);
138         EuclideanTestUtils.assertVertexLoopSequence(Arrays.asList(p3, p1, p2), tris.get(3), TEST_PRECISION);
139     }
140 
141     @Test
142     void testConvexPolygonToTriangleFan_notEnoughVertices() {
143         // arrange
144         final String baseMsg = "Cannot create triangle fan: 3 or more vertices are required but found only ";
145 
146         // act/assert
147         GeometryTestUtils.assertThrowsWithMessage(() -> {
148             EuclideanUtils.convexPolygonToTriangleFan(Collections.emptyList(), Function.identity());
149         }, IllegalArgumentException.class, baseMsg + "0");
150 
151         GeometryTestUtils.assertThrowsWithMessage(() -> {
152             EuclideanUtils.convexPolygonToTriangleFan(Collections.singletonList(Vector3D.ZERO), Function.identity());
153         }, IllegalArgumentException.class, baseMsg + "1");
154 
155         GeometryTestUtils.assertThrowsWithMessage(() -> {
156             EuclideanUtils.convexPolygonToTriangleFan(Arrays.asList(Vector3D.ZERO, Vector3D.of(1, 0, 0)), Function.identity());
157         }, IllegalArgumentException.class, baseMsg + "2");
158     }
159 }