1   /* Copyright 2002-2024 CS GROUP
2    * Licensed to CS GROUP (CS) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * CS 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.orekit.geometry.fov;
18  
19  import org.hipparchus.exception.LocalizedCoreFormats;
20  import org.hipparchus.geometry.euclidean.threed.Rotation;
21  import org.hipparchus.geometry.euclidean.threed.RotationConvention;
22  import org.hipparchus.geometry.euclidean.threed.Vector3D;
23  import org.hipparchus.geometry.partitioning.Region;
24  import org.hipparchus.geometry.partitioning.RegionFactory;
25  import org.hipparchus.geometry.spherical.twod.Sphere2D;
26  import org.hipparchus.geometry.spherical.twod.SphericalPolygonsSet;
27  import org.hipparchus.util.FastMath;
28  import org.orekit.errors.OrekitException;
29  
30  /** Class representing a spacecraft sensor Field Of View with dihedral shape (i.e. rectangular shape).
31   * @author Luc Maisonobe
32   * @since 10.1
33   */
34  public class DoubleDihedraFieldOfView extends PolygonalFieldOfView {
35  
36      /** Build a Field Of View with dihedral shape (i.e. rectangular shape).
37       * @param center Direction of the FOV center, in spacecraft frame
38       * @param axis1 FOV dihedral axis 1, in spacecraft frame
39       * @param halfAperture1 FOV dihedral half aperture angle 1,
40       * must be less than π/2, i.e. full dihedra must be smaller then
41       * an hemisphere
42       * @param axis2 FOV dihedral axis 2, in spacecraft frame
43       * @param halfAperture2 FOV dihedral half aperture angle 2,
44       * must be less than π/2, i.e. full dihedra must be smaller then
45       * an hemisphere
46       * @param margin angular margin to apply to the zone (if positive,
47       * points outside of the raw FoV but close enough to the boundary are
48       * considered visible; if negative, points inside of the raw FoV
49       * but close enough to the boundary are considered not visible)
50       */
51      public DoubleDihedraFieldOfView(final Vector3D center,
52                                      final Vector3D axis1, final double halfAperture1,
53                                      final Vector3D axis2, final double halfAperture2,
54                                      final double margin) {
55          super(createPolygon(center, axis1, halfAperture1, axis2, halfAperture2), margin);
56      }
57  
58      /** Create polygon.
59       * @param center Direction of the FOV center, in spacecraft frame
60       * @param axis1 FOV dihedral axis 1, in spacecraft frame
61       * @param halfAperture1 FOV dihedral half aperture angle 1,
62       * must be less than π/2, i.e. full dihedra must be smaller then
63       * an hemisphere
64       * @param axis2 FOV dihedral axis 2, in spacecraft frame
65       * @param halfAperture2 FOV dihedral half aperture angle 2,
66       * must be less than π/2, i.e. full dihedra must be smaller then
67       * an hemisphere
68       * @return built polygon
69       */
70      private static SphericalPolygonsSet createPolygon(final Vector3D center,
71                                                        final Vector3D axis1, final double halfAperture1,
72                                                        final Vector3D axis2, final double halfAperture2) {
73          final RegionFactory<Sphere2D> factory = new RegionFactory<Sphere2D>();
74          final double tolerance = FastMath.max(FastMath.ulp(2.0 * FastMath.PI),
75                                                1.0e-12 * FastMath.max(halfAperture1, halfAperture2));
76          final Region<Sphere2D> dihedra1 = buildDihedra(factory, tolerance, center, axis1, halfAperture1);
77          final Region<Sphere2D> dihedra2 = buildDihedra(factory, tolerance, center, axis2, halfAperture2);
78          return (SphericalPolygonsSet) factory.intersection(dihedra1, dihedra2);
79      }
80  
81      /** Build a dihedra.
82       * @param factory factory for regions
83       * @param tolerance tolerance below which points are considered equal
84       * @param center Direction of the FOV center, in spacecraft frame
85       * @param axis FOV dihedral axis, in spacecraft frame
86       * @param halfAperture FOV dihedral half aperture angle,
87       * must be less than π/2, i.e. full dihedra must be smaller then
88       * an hemisphere
89       * @return dihedra
90       */
91      private static Region<Sphere2D> buildDihedra(final RegionFactory<Sphere2D> factory,
92                                                   final double tolerance, final Vector3D center,
93                                                   final Vector3D axis, final double halfAperture) {
94          if (halfAperture > 0.5 * FastMath.PI) {
95              throw new OrekitException(LocalizedCoreFormats.OUT_OF_RANGE_SIMPLE,
96                                        halfAperture, 0.0, 0.5 * FastMath.PI);
97          }
98  
99          final Rotation r = new Rotation(axis, halfAperture, RotationConvention.VECTOR_OPERATOR);
100         final Vector3D normalCenterPlane = Vector3D.crossProduct(axis, center);
101         final Vector3D normalSidePlus    = r.applyInverseTo(normalCenterPlane);
102         final Vector3D normalSideMinus   = r.applyTo(normalCenterPlane.negate());
103 
104         return factory.intersection(new SphericalPolygonsSet(normalSidePlus,  tolerance),
105                                     new SphericalPolygonsSet(normalSideMinus, tolerance));
106 
107     }
108 
109 }