FACT++  1.0
rv2m.c
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1 #include "erfa.h"
2 
3 void eraRv2m(double w[3], double r[3][3])
4 /*
5 ** - - - - - - - -
6 ** e r a R v 2 m
7 ** - - - - - - - -
8 **
9 ** Form the r-matrix corresponding to a given r-vector.
10 **
11 ** Given:
12 ** w double[3] rotation vector (Note 1)
13 **
14 ** Returned:
15 ** r double[3][3] rotation matrix
16 **
17 ** Notes:
18 **
19 ** 1) A rotation matrix describes a rotation through some angle about
20 ** some arbitrary axis called the Euler axis. The "rotation vector"
21 ** supplied to This function has the same direction as the Euler
22 ** axis, and its magnitude is the angle in radians.
23 **
24 ** 2) If w is null, the unit matrix is returned.
25 **
26 ** 3) The reference frame rotates clockwise as seen looking along the
27 ** rotation vector from the origin.
28 **
29 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
30 ** Derived, with permission, from the SOFA library. See notes at end of file.
31 */
32 {
33  double x, y, z, phi, s, c, f;
34 
35 
36 /* Euler angle (magnitude of rotation vector) and functions. */
37  x = w[0];
38  y = w[1];
39  z = w[2];
40  phi = sqrt(x*x + y*y + z*z);
41  s = sin(phi);
42  c = cos(phi);
43  f = 1.0 - c;
44 
45 /* Euler axis (direction of rotation vector), perhaps null. */
46  if (phi > 0.0) {
47  x /= phi;
48  y /= phi;
49  z /= phi;
50  }
51 
52 /* Form the rotation matrix. */
53  r[0][0] = x*x*f + c;
54  r[0][1] = x*y*f + z*s;
55  r[0][2] = x*z*f - y*s;
56  r[1][0] = y*x*f - z*s;
57  r[1][1] = y*y*f + c;
58  r[1][2] = y*z*f + x*s;
59  r[2][0] = z*x*f + y*s;
60  r[2][1] = z*y*f - x*s;
61  r[2][2] = z*z*f + c;
62 
63  return;
64 
65 }
66 /*----------------------------------------------------------------------
67 **
68 **
69 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
70 ** All rights reserved.
71 **
72 ** This library is derived, with permission, from the International
73 ** Astronomical Union's "Standards of Fundamental Astronomy" library,
74 ** available from http://www.iausofa.org.
75 **
76 ** The ERFA version is intended to retain identical functionality to
77 ** the SOFA library, but made distinct through different function and
78 ** file names, as set out in the SOFA license conditions. The SOFA
79 ** original has a role as a reference standard for the IAU and IERS,
80 ** and consequently redistribution is permitted only in its unaltered
81 ** state. The ERFA version is not subject to this restriction and
82 ** therefore can be included in distributions which do not support the
83 ** concept of "read only" software.
84 **
85 ** Although the intent is to replicate the SOFA API (other than
86 ** replacement of prefix names) and results (with the exception of
87 ** bugs; any that are discovered will be fixed), SOFA is not
88 ** responsible for any errors found in this version of the library.
89 **
90 ** If you wish to acknowledge the SOFA heritage, please acknowledge
91 ** that you are using a library derived from SOFA, rather than SOFA
92 ** itself.
93 **
94 **
95 ** TERMS AND CONDITIONS
96 **
97 ** Redistribution and use in source and binary forms, with or without
98 ** modification, are permitted provided that the following conditions
99 ** are met:
100 **
101 ** 1 Redistributions of source code must retain the above copyright
102 ** notice, this list of conditions and the following disclaimer.
103 **
104 ** 2 Redistributions in binary form must reproduce the above copyright
105 ** notice, this list of conditions and the following disclaimer in
106 ** the documentation and/or other materials provided with the
107 ** distribution.
108 **
109 ** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
110 ** the International Astronomical Union nor the names of its
111 ** contributors may be used to endorse or promote products derived
112 ** from this software without specific prior written permission.
113 **
114 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
115 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
116 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
117 ** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
118 ** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
119 ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
120 ** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
121 ** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
122 ** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
123 ** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
124 ** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
125 ** POSSIBILITY OF SUCH DAMAGE.
126 **
127 */
eraRv2m
void eraRv2m(double w[3], double r[3][3])
Definition: rv2m.c:3