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.threed.rotation;
18
19 /** Enum defining the possible reference frames for locating axis
20 * positions during a rotation sequence.
21 */
22 public enum AxisReferenceFrame {
23
24 /** Defines a relative reference frame for a rotation sequence. Sequences
25 * with this type of reference frame are called <em>intrinsic rotations</em>.
26 *
27 * <p>
28 * When using a relative reference frame, each successive axis
29 * is located relative to the "thing" being rotated and not to some
30 * external frame of reference. For example, say that a rotation sequence
31 * is defined around the {@code x}, {@code y}, and {@code z} axes in
32 * that order. The first rotation will occur around the standard {@code x}
33 * axis. The second rotation, however, will occur around the {@code y}
34 * axis after it has been rotated by the first rotation; we can call this
35 * new axis {@code y'}. Similarly, the third rotation will occur around
36 * {@code z''}, which may or may not match the original {@code z} axis.
37 * A good real-world example of this type of situation is an airplane,
38 * where a pilot makes a sequence of rotations in order, with each rotation
39 * using the airplane's own up/down, left/right, back/forward directions
40 * as the frame of reference.
41 * </p>
42 */
43 RELATIVE,
44
45 /** Defines an absolute reference frame for a rotation sequence. Sequences
46 * with this type of reference frame are called <em>extrinsic rotations</em>.
47 *
48 * <p>
49 * In contrast with the relative reference frame, the absolute reference frame
50 * remains fixed throughout a rotation sequence, with each rotation axis not
51 * affected by the rotations.
52 * </p>
53 */
54 ABSOLUTE
55 }