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#include "erfa.h"
void eraRv2m(double w[3], double r[3][3])
/*
** - - - - - - - -
** e r a R v 2 m
** - - - - - - - -
**
** Form the r-matrix corresponding to a given r-vector.
**
** Given:
** w double[3] rotation vector (Note 1)
**
** Returned:
** r double[3][3] rotation matrix
**
** Notes:
**
** 1) A rotation matrix describes a rotation through some angle about
** some arbitrary axis called the Euler axis. The "rotation vector"
** supplied to This function has the same direction as the Euler
** axis, and its magnitude is the angle in radians.
**
** 2) If w is null, the unit matrix is returned.
**
** 3) The reference frame rotates clockwise as seen looking along the
** rotation vector from the origin.
**
** Copyright (C) 2013-2016, NumFOCUS Foundation.
** Derived, with permission, from the SOFA library. See notes at end of file.
*/
{
double x, y, z, phi, s, c, f;
/* Euler angle (magnitude of rotation vector) and functions. */
x = w[0];
y = w[1];
z = w[2];
phi = sqrt(x*x + y*y + z*z);
s = sin(phi);
c = cos(phi);
f = 1.0 - c;
/* Euler axis (direction of rotation vector), perhaps null. */
if (phi > 0.0) {
x /= phi;
y /= phi;
z /= phi;
}
/* Form the rotation matrix. */
r[0][0] = x*x*f + c;
r[0][1] = x*y*f + z*s;
r[0][2] = x*z*f - y*s;
r[1][0] = y*x*f - z*s;
r[1][1] = y*y*f + c;
r[1][2] = y*z*f + x*s;
r[2][0] = z*x*f + y*s;
r[2][1] = z*y*f - x*s;
r[2][2] = z*z*f + c;
return;
}
/*----------------------------------------------------------------------
**
**
** Copyright (C) 2013-2016, NumFOCUS Foundation.
** All rights reserved.
**
** This library is derived, with permission, from the International
** Astronomical Union's "Standards of Fundamental Astronomy" library,
** available from http://www.iausofa.org.
**
** The ERFA version is intended to retain identical functionality to
** the SOFA library, but made distinct through different function and
** file names, as set out in the SOFA license conditions. The SOFA
** original has a role as a reference standard for the IAU and IERS,
** and consequently redistribution is permitted only in its unaltered
** state. The ERFA version is not subject to this restriction and
** therefore can be included in distributions which do not support the
** concept of "read only" software.
**
** Although the intent is to replicate the SOFA API (other than
** replacement of prefix names) and results (with the exception of
** bugs; any that are discovered will be fixed), SOFA is not
** responsible for any errors found in this version of the library.
**
** If you wish to acknowledge the SOFA heritage, please acknowledge
** that you are using a library derived from SOFA, rather than SOFA
** itself.
**
**
** TERMS AND CONDITIONS
**
** Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions
** are met:
**
** 1 Redistributions of source code must retain the above copyright
** notice, this list of conditions and the following disclaimer.
**
** 2 Redistributions in binary form must reproduce the above copyright
** notice, this list of conditions and the following disclaimer in
** the documentation and/or other materials provided with the
** distribution.
**
** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
** the International Astronomical Union nor the names of its
** contributors may be used to endorse or promote products derived
** from this software without specific prior written permission.
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
** POSSIBILITY OF SUCH DAMAGE.
**
*/
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