1   /* Copyright 2022-2026 Romain Serra
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.propagation.events.functions;
18  
19  import org.hipparchus.CalculusFieldElement;
20  import org.hipparchus.geometry.euclidean.threed.Vector3D;
21  import org.orekit.frames.Frame;
22  import org.orekit.propagation.FieldSpacecraftState;
23  import org.orekit.propagation.SpacecraftState;
24  
25  /** Event function for crossing a 2D plane in 3D space, as defined by a normal vector.
26   * The plane is assumed to contain the origin of the frame where the normal's coordinates are given.
27   * The event function is negative under the plane according to the normal's orientation.
28   * @author Romain Serra
29   * @since 14.0
30   */
31  public class PlaneCrossingFunction implements EventFunction {
32  
33      /** Plane normal vector. */
34      private final Vector3D planeNormal;
35  
36      /** Plane reference frame. */
37      private final Frame planeFrame;
38  
39      /** Constructor.
40       * @param normal plane normal
41       * @param frame plane frame
42       */
43      public PlaneCrossingFunction(final Vector3D normal, final Frame frame) {
44          this.planeNormal = normal.normalize();
45          this.planeFrame = frame;
46      }
47  
48      /**
49       * Getter for the plane frame.
50       * @return frame
51       */
52      public Frame getPlaneFrame() {
53          return planeFrame;
54      }
55  
56      /**
57       * Getter for the plane normal vector.
58       * @return normal
59       */
60      public Vector3D getPlaneNormal() {
61          return planeNormal;
62      }
63  
64      @Override
65      public double value(final SpacecraftState state) {
66          return state.getPosition(planeFrame).dotProduct(planeNormal);
67      }
68  
69      @Override
70      public <T extends CalculusFieldElement<T>> T value(final FieldSpacecraftState<T> fieldState) {
71          return fieldState.getPosition(planeFrame).dotProduct(planeNormal);
72      }
73  
74  }