ImathEuler.h

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//
// SPDX-License-Identifier: BSD-3-Clause
// Copyright Contributors to the OpenEXR Project.
//

//
// Euler angle representation of rotation/orientation
//

#ifndef INCLUDED_IMATHEULER_H
#define INCLUDED_IMATHEULER_H

#include "ImathExport.h"
#include "ImathNamespace.h"

#include "ImathMath.h"
#include "ImathMatrix.h"
#include "ImathQuat.h"
#include "ImathVec.h"

#include <iostream>

IMATH_INTERNAL_NAMESPACE_HEADER_ENTER

#if (defined _WIN32 || defined _WIN64) && defined _MSC_VER
// Disable MS VC++ warnings about conversion from double to float
#    pragma warning(push)
#    pragma warning(disable : 4244)
#endif

///
/// Template class `Euler<T>`
///
/// The Euler class represents euler angle orientations. The class
/// inherits from Vec3 to it can be freely cast. The additional
/// information is the euler priorities rep. This class is
/// essentially a rip off of Ken Shoemake's GemsIV code. It has
/// been modified minimally to make it more understandable, but
/// hardly enough to make it easy to grok completely.
///
/// There are 24 possible combonations of Euler angle
/// representations of which 12 are common in CG and you will
/// probably only use 6 of these which in this scheme are the
/// non-relative-non-repeating types.
///
/// The representations can be partitioned according to two
/// criteria:
///
///    1) Are the angles measured relative to a set of fixed axis
///       or relative to each other (the latter being what happens
///       when rotation matrices are multiplied together and is
///       almost ubiquitous in the cg community)
///
///    2) Is one of the rotations repeated (ala XYX rotation)
///
/// When you construct a given representation from scratch you
/// must order the angles according to their priorities. So, the
/// easiest is a softimage or aerospace (yaw/pitch/roll) ordering
/// of ZYX.
///
///     float x_rot = 1;
///     float y_rot = 2;
///     float z_rot = 3;
///
///     Eulerf angles(z_rot, y_rot, x_rot, Eulerf::ZYX);
///
/// or:
///
///     Eulerf angles( V3f(z_rot,y_rot,z_rot), Eulerf::ZYX );
///
///
/// If instead, the order was YXZ for instance you would have to
/// do this:
///
///     float x_rot = 1;
///     float y_rot = 2;
///     float z_rot = 3;
///
///     Eulerf angles(y_rot, x_rot, z_rot, Eulerf::YXZ);
///
/// or:
///
///
///     Eulerf angles( V3f(y_rot,x_rot,z_rot), Eulerf::YXZ );
///
/// Notice how the order you put the angles into the three slots
/// should correspond to the enum (YXZ) ordering. The input angle
/// vector is called the "ijk" vector -- not an "xyz" vector. The
/// ijk vector order is the same as the enum. If you treat the
/// Euler as a Vec3 (which it inherts from) you will find the
/// angles are ordered in the same way, i.e.:
///
///     V3f v = angles;
///     v.x == y_rot, v.y == x_rot, v.z == z_rot
///
/// If you just want the x, y, and z angles stored in a vector in
/// that order, you can do this:
///
///     V3f v = angles.toXYZVector()
///     v.x == x_rot, v.y == y_rot, v.z == z_rot
///
/// If you want to set the Euler with an XYZVector use the
/// optional layout argument:
///
///     Eulerf angles(x_rot, y_rot, z_rot, Eulerf::YXZ, Eulerf::XYZLayout);
///
/// This is the same as:
///
///     Eulerf angles(y_rot, x_rot, z_rot, Eulerf::YXZ);
///
/// Note that this won't do anything intelligent if you have a
/// repeated axis in the euler angles (e.g. XYX)
///
/// If you need to use the "relative" versions of these, you will
/// need to use the "r" enums.
///
/// The units of the rotation angles are assumed to be radians.
///

template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Euler : public Vec3<T>
{
  public:
    using Vec3<T>::x;
    using Vec3<T>::y;
    using Vec3<T>::z;

    
    ///
    ///  All 24 possible orderings
    ///
    enum IMATH_EXPORT_ENUM Order
    {
        XYZ = 0x0101, // "usual" orderings
        XZY = 0x0001,
        YZX = 0x1101,
        YXZ = 0x1001,
        ZXY = 0x2101,
        ZYX = 0x2001,

        XZX = 0x0011, // first axis repeated
        XYX = 0x0111,
        YXY = 0x1011,
        YZY = 0x1111,
        ZYZ = 0x2011,
        ZXZ = 0x2111,

        XYZr = 0x2000, // relative orderings -- not common
        XZYr = 0x2100,
        YZXr = 0x1000,
        YXZr = 0x1100,
        ZXYr = 0x0000,
        ZYXr = 0x0100,

        XZXr = 0x2110, // relative first axis repeated
        XYXr = 0x2010,
        YXYr = 0x1110,
        YZYr = 0x1010,
        ZYZr = 0x0110,
        ZXZr = 0x0010,
        //       ||||
        //       VVVV
        //       ABCD
        // Legend: 
        //  A -> Initial Axis (0==x, 1==y, 2==z)
        //  B -> Parity Even (1==true)
        //  C -> Initial Repeated (1==true)
        //  D -> Frame Static (1==true)
        //

        Legal = XYZ | XZY | YZX | YXZ | ZXY | ZYX | XZX | XYX | YXY | YZY | ZYZ | ZXZ | XYZr |
                XZYr | YZXr | YXZr | ZXYr | ZYXr | XZXr | XYXr | YXYr | YZYr | ZYZr | ZXZr,

        Min     = 0x0000,
        Max     = 0x2111,
        Default = XYZ
    };

    ///
    /// Axes
    ///
    enum IMATH_EXPORT_ENUM Axis
    {
        X = 0,
        Y = 1,
        Z = 2
    };

    ///
    /// Layout
    ///
    
    enum IMATH_EXPORT_ENUM InputLayout
    {
        XYZLayout,
        IJKLayout
    };

    /// @{
    /// @name Constructors
    ///
    /// All default to `ZYX` non-relative (ala Softimage 3D/Maya),
    /// where there is no argument to specify it.
    ///
    /// The Euler-from-matrix constructors assume that the matrix does
    /// not include shear or non-uniform scaling, but the constructors
    /// do not examine the matrix to verify this assumption.  If necessary,
    /// you can adjust the matrix by calling the removeScalingAndShear()
    /// function, defined in ImathMatrixAlgo.h.

    /// No initialization by default
    IMATH_HOSTDEVICE constexpr Euler() IMATH_NOEXCEPT;

    /// Copy constructor
    IMATH_HOSTDEVICE IMATH_CONSTEXPR14 Euler (const Euler&) IMATH_NOEXCEPT;

    /// Construct from given Order
    IMATH_HOSTDEVICE IMATH_CONSTEXPR14 Euler (Order p) IMATH_NOEXCEPT;

    /// Construct from vector, order, layout
    IMATH_HOSTDEVICE IMATH_CONSTEXPR14 Euler (const Vec3<T>& v,
                                              Order o       = Default,
                                              InputLayout l = IJKLayout) IMATH_NOEXCEPT;
    /// Construct from explicit axes, order, layout
    IMATH_HOSTDEVICE IMATH_CONSTEXPR14
    Euler (T i, T j, T k, Order o = Default, InputLayout l = IJKLayout) IMATH_NOEXCEPT;

    /// Copy constructor with new Order
    IMATH_HOSTDEVICE IMATH_CONSTEXPR14 Euler (const Euler<T>& euler, Order newp) IMATH_NOEXCEPT;

    /// Construct from Matrix33
    IMATH_HOSTDEVICE IMATH_CONSTEXPR14 Euler (const Matrix33<T>&, Order o = Default) IMATH_NOEXCEPT;

    /// Construct from Matrix44
    IMATH_HOSTDEVICE IMATH_CONSTEXPR14 Euler (const Matrix44<T>&, Order o = Default) IMATH_NOEXCEPT;

    /// Destructor
    IMATH_HOSTDEVICE ~Euler() = default;

    /// @}
    
    /// @{
    /// @name Query
    
    /// Return whether the given value is a legal Order
    IMATH_HOSTDEVICE constexpr static bool legal (Order) IMATH_NOEXCEPT;

    /// Return the order
    IMATH_HOSTDEVICE IMATH_CONSTEXPR14 Order order() const IMATH_NOEXCEPT;

    /// Return frameStatic
    IMATH_HOSTDEVICE constexpr bool frameStatic() const { return _frameStatic; }

    /// Return intialRepeated
    IMATH_HOSTDEVICE constexpr bool initialRepeated() const { return _initialRepeated; }

    /// Return partityEven
    IMATH_HOSTDEVICE constexpr bool parityEven() const { return _parityEven; }

    /// Return initialAxis 
    IMATH_HOSTDEVICE constexpr Axis initialAxis() const { return _initialAxis; }

    /// Unpack angles from ijk form
    IMATH_HOSTDEVICE void angleOrder (int& i, int& j, int& k) const IMATH_NOEXCEPT;

    /// Determine mapping from xyz to ijk (reshuffle the xyz to match the order)
    IMATH_HOSTDEVICE void angleMapping (int& i, int& j, int& k) const IMATH_NOEXCEPT;

    /// @}

    /// @{
    /// @name Set Value
    
    /// Set the order. This does NOT convert the angles, but it
    /// does reorder the input vector.
    IMATH_HOSTDEVICE void setOrder (Order) IMATH_NOEXCEPT;

    /// Set the euler value: set the first angle to `v[0]`, the second to
    /// `v[1]`, the third to `v[2]`.
    IMATH_HOSTDEVICE void setXYZVector (const Vec3<T>&) IMATH_NOEXCEPT;

    /// Set the value.
    IMATH_HOSTDEVICE void set (Axis initial, bool relative, bool parityEven, bool firstRepeats) IMATH_NOEXCEPT;

    /// @}
    
    /// @{
    /// @name Assignments and Conversions
    ///

    /// Assignment
    IMATH_HOSTDEVICE IMATH_CONSTEXPR14 const Euler<T>& operator= (const Euler<T>&) IMATH_NOEXCEPT;

    /// Assignment
    IMATH_HOSTDEVICE IMATH_CONSTEXPR14 const Euler<T>& operator= (const Vec3<T>&) IMATH_NOEXCEPT;

    /// Assign from Matrix33, assumed to be affine
    IMATH_HOSTDEVICE void extract (const Matrix33<T>&) IMATH_NOEXCEPT;

    /// Assign from Matrix44, assumed to be affine
    IMATH_HOSTDEVICE void extract (const Matrix44<T>&) IMATH_NOEXCEPT;

    /// Assign from Quaternion
    IMATH_HOSTDEVICE void extract (const Quat<T>&) IMATH_NOEXCEPT;

    /// Convert to Matrix33
    IMATH_HOSTDEVICE Matrix33<T> toMatrix33() const IMATH_NOEXCEPT;

    /// Convert to Matrix44
    IMATH_HOSTDEVICE Matrix44<T> toMatrix44() const IMATH_NOEXCEPT;

    /// Convert to Quat
    IMATH_HOSTDEVICE Quat<T> toQuat() const IMATH_NOEXCEPT;

    /// Reorder the angles so that the X rotation comes first,
    ///  followed by the Y and Z in cases like XYX ordering, the
    ///  repeated angle will be in the "z" component
    IMATH_HOSTDEVICE Vec3<T> toXYZVector() const IMATH_NOEXCEPT;

    /// @}
    
    /// @{
    /// @name Utility Methods
    ///
    ///  Utility methods for getting continuous rotations. None of these
    ///  methods change the orientation given by its inputs (or at least
    ///  that is the intent).

    /// Convert an angle to its equivalent in [-PI, PI]
    IMATH_HOSTDEVICE IMATH_CONSTEXPR14 static float angleMod (T angle) IMATH_NOEXCEPT;

    /// Adjust xyzRot so that its components differ from targetXyzRot by no more than +/-PI
    IMATH_HOSTDEVICE static void simpleXYZRotation (Vec3<T>& xyzRot, const Vec3<T>& targetXyzRot) IMATH_NOEXCEPT;

    /// Adjust xyzRot so that its components differ from targetXyzRot by as little as possible.
    /// Note that xyz here really means ijk, because the order must be provided.
    IMATH_HOSTDEVICE static void
    nearestRotation (Vec3<T>& xyzRot, const Vec3<T>& targetXyzRot, Order order = XYZ) IMATH_NOEXCEPT;

    /// Adjusts "this" Euler so that its components differ from target
    /// by as little as possible. This method might not make sense for
    /// Eulers with different order and it probably doesn't work for
    /// repeated axis and relative orderings (TODO).
    IMATH_HOSTDEVICE void makeNear (const Euler<T>& target) IMATH_NOEXCEPT;

    /// @}

  protected:

    /// relative or static rotations
    bool _frameStatic : 1;     

    /// init axis repeated as last
    bool _initialRepeated : 1; 

    /// "parity of axis permutation"
    bool _parityEven : 1;      

#if defined _WIN32 || defined _WIN64
    /// First axis of rotation
    Axis _initialAxis; 
#else
    /// First axis of rotation
    Axis _initialAxis : 2; 
#endif
};

//
// Convenient typedefs
//

/// Euler of type float
typedef Euler<float> Eulerf;
/// Euler of type double
typedef Euler<double> Eulerd;

//
// Implementation
//

/// @cond Doxygen_Suppress

template <class T>
IMATH_HOSTDEVICE inline void
Euler<T>::angleOrder (int& i, int& j, int& k) const IMATH_NOEXCEPT
{
    i = _initialAxis;
    j = _parityEven ? (i + 1) % 3 : (i > 0 ? i - 1 : 2);
    k = _parityEven ? (i > 0 ? i - 1 : 2) : (i + 1) % 3;
}

template <class T>
IMATH_HOSTDEVICE inline void
Euler<T>::angleMapping (int& i, int& j, int& k) const IMATH_NOEXCEPT
{
    int m[3];

    m[_initialAxis]           = 0;
    m[(_initialAxis + 1) % 3] = _parityEven ? 1 : 2;
    m[(_initialAxis + 2) % 3] = _parityEven ? 2 : 1;
    i                         = m[0];
    j                         = m[1];
    k                         = m[2];
}

template <class T>
IMATH_HOSTDEVICE inline void
Euler<T>::setXYZVector (const Vec3<T>& v) IMATH_NOEXCEPT
{
    int i, j, k;
    angleMapping (i, j, k);
    (*this)[i] = v.x;
    (*this)[j] = v.y;
    (*this)[k] = v.z;
}

template <class T>
IMATH_HOSTDEVICE inline Vec3<T>
Euler<T>::toXYZVector() const IMATH_NOEXCEPT
{
    int i, j, k;
    angleMapping (i, j, k);
    return Vec3<T> ((*this)[i], (*this)[j], (*this)[k]);
}

template <class T>
IMATH_HOSTDEVICE constexpr inline Euler<T>::Euler() IMATH_NOEXCEPT
    : Vec3<T> (0, 0, 0),
      _frameStatic (true),
      _initialRepeated (false),
      _parityEven (true),
      _initialAxis (X)
{}

template <class T>
IMATH_HOSTDEVICE IMATH_CONSTEXPR14 inline Euler<T>::Euler (typename Euler<T>::Order p) IMATH_NOEXCEPT
    : Vec3<T> (0, 0, 0),
      _frameStatic (true),
      _initialRepeated (false),
      _parityEven (true),
      _initialAxis (X)
{
    setOrder (p);
}

template <class T>
IMATH_HOSTDEVICE IMATH_CONSTEXPR14 inline Euler<T>::Euler (const Vec3<T>& v,
                                          typename Euler<T>::Order p,
                                          typename Euler<T>::InputLayout l) IMATH_NOEXCEPT
{
    setOrder (p);
    if (l == XYZLayout)
        setXYZVector (v);
    else
    {
        x = v.x;
        y = v.y;
        z = v.z;
    }
}

template <class T>
IMATH_HOSTDEVICE IMATH_CONSTEXPR14 inline Euler<T>::Euler (const Euler<T>& euler) IMATH_NOEXCEPT
{
    operator= (euler);
}

template <class T>
IMATH_HOSTDEVICE IMATH_CONSTEXPR14 inline Euler<T>::Euler (const Euler<T>& euler, Order p) IMATH_NOEXCEPT
{
    setOrder (p);
    Matrix33<T> M = euler.toMatrix33();
    extract (M);
}

template <class T>
IMATH_HOSTDEVICE IMATH_CONSTEXPR14 inline
Euler<T>::Euler (T xi, T yi, T zi, typename Euler<T>::Order p,
                 typename Euler<T>::InputLayout l) IMATH_NOEXCEPT
{
    setOrder (p);
    if (l == XYZLayout)
        setXYZVector (Vec3<T> (xi, yi, zi));
    else
    {
        x = xi;
        y = yi;
        z = zi;
    }
}

template <class T>
IMATH_HOSTDEVICE IMATH_CONSTEXPR14 inline Euler<T>::Euler (const Matrix33<T>& M, typename Euler::Order p) IMATH_NOEXCEPT
{
    setOrder (p);
    extract (M);
}

template <class T>
IMATH_HOSTDEVICE IMATH_CONSTEXPR14 inline Euler<T>::Euler (const Matrix44<T>& M, typename Euler::Order p) IMATH_NOEXCEPT
{
    setOrder (p);
    extract (M);
}

template <class T>
IMATH_HOSTDEVICE inline void
Euler<T>::extract (const Quat<T>& q) IMATH_NOEXCEPT
{
    extract (q.toMatrix33());
}

template <class T>
IMATH_HOSTDEVICE void
Euler<T>::extract (const Matrix33<T>& M) IMATH_NOEXCEPT
{
    int i, j, k;
    angleOrder (i, j, k);

    if (_initialRepeated)
    {
        //
        // Extract the first angle, x.
        //

        x = std::atan2 (M[j][i], M[k][i]);

        //
        // Remove the x rotation from M, so that the remaining
        // rotation, N, is only around two axes, and gimbal lock
        // cannot occur.
        //

        Vec3<T> r (0, 0, 0);
        r[i] = (_parityEven ? -x : x);

        Matrix44<T> N;
        N.rotate (r);

        N = N * Matrix44<T> (M[0][0],
                             M[0][1],
                             M[0][2],
                             0,
                             M[1][0],
                             M[1][1],
                             M[1][2],
                             0,
                             M[2][0],
                             M[2][1],
                             M[2][2],
                             0,
                             0,
                             0,
                             0,
                             1);
        //
        // Extract the other two angles, y and z, from N.
        //

        T sy = std::sqrt (N[j][i] * N[j][i] + N[k][i] * N[k][i]);
        y    = std::atan2 (sy, N[i][i]);
        z    = std::atan2 (N[j][k], N[j][j]);
    }
    else
    {
        //
        // Extract the first angle, x.
        //

        x = std::atan2 (M[j][k], M[k][k]);

        //
        // Remove the x rotation from M, so that the remaining
        // rotation, N, is only around two axes, and gimbal lock
        // cannot occur.
        //

        Vec3<T> r (0, 0, 0);
        r[i] = (_parityEven ? -x : x);

        Matrix44<T> N;
        N.rotate (r);

        N = N * Matrix44<T> (M[0][0],
                             M[0][1],
                             M[0][2],
                             0,
                             M[1][0],
                             M[1][1],
                             M[1][2],
                             0,
                             M[2][0],
                             M[2][1],
                             M[2][2],
                             0,
                             0,
                             0,
                             0,
                             1);
        //
        // Extract the other two angles, y and z, from N.
        //

        T cy = std::sqrt (N[i][i] * N[i][i] + N[i][j] * N[i][j]);
        y    = std::atan2 (-N[i][k], cy);
        z    = std::atan2 (-N[j][i], N[j][j]);
    }

    if (!_parityEven)
        *this *= -1;

    if (!_frameStatic)
    {
        T t = x;
        x   = z;
        z   = t;
    }
}

template <class T>
IMATH_HOSTDEVICE void
Euler<T>::extract (const Matrix44<T>& M) IMATH_NOEXCEPT
{
    int i, j, k;
    angleOrder (i, j, k);

    if (_initialRepeated)
    {
        //
        // Extract the first angle, x.
        //

        x = std::atan2 (M[j][i], M[k][i]);

        //
        // Remove the x rotation from M, so that the remaining
        // rotation, N, is only around two axes, and gimbal lock
        // cannot occur.
        //

        Vec3<T> r (0, 0, 0);
        r[i] = (_parityEven ? -x : x);

        Matrix44<T> N;
        N.rotate (r);
        N = N * M;

        //
        // Extract the other two angles, y and z, from N.
        //

        T sy = std::sqrt (N[j][i] * N[j][i] + N[k][i] * N[k][i]);
        y    = std::atan2 (sy, N[i][i]);
        z    = std::atan2 (N[j][k], N[j][j]);
    }
    else
    {
        //
        // Extract the first angle, x.
        //

        x = std::atan2 (M[j][k], M[k][k]);

        //
        // Remove the x rotation from M, so that the remaining
        // rotation, N, is only around two axes, and gimbal lock
        // cannot occur.
        //

        Vec3<T> r (0, 0, 0);
        r[i] = (_parityEven ? -x : x);

        Matrix44<T> N;
        N.rotate (r);
        N = N * M;

        //
        // Extract the other two angles, y and z, from N.
        //

        T cy = std::sqrt (N[i][i] * N[i][i] + N[i][j] * N[i][j]);
        y    = std::atan2 (-N[i][k], cy);
        z    = std::atan2 (-N[j][i], N[j][j]);
    }

    if (!_parityEven)
        *this *= -1;

    if (!_frameStatic)
    {
        T t = x;
        x   = z;
        z   = t;
    }
}

template <class T>
IMATH_HOSTDEVICE Matrix33<T>
Euler<T>::toMatrix33() const IMATH_NOEXCEPT
{
    int i, j, k;
    angleOrder (i, j, k);

    Vec3<T> angles;

    if (_frameStatic)
        angles = (*this);
    else
        angles = Vec3<T> (z, y, x);

    if (!_parityEven)
        angles *= -1.0;

    T ci = std::cos (angles.x);
    T cj = std::cos (angles.y);
    T ch = std::cos (angles.z);
    T si = std::sin (angles.x);
    T sj = std::sin (angles.y);
    T sh = std::sin (angles.z);

    T cc = ci * ch;
    T cs = ci * sh;
    T sc = si * ch;
    T ss = si * sh;

    Matrix33<T> M;

    if (_initialRepeated)
    {
        M[i][i] = cj;
        M[j][i] = sj * si;
        M[k][i] = sj * ci;
        M[i][j] = sj * sh;
        M[j][j] = -cj * ss + cc;
        M[k][j] = -cj * cs - sc;
        M[i][k] = -sj * ch;
        M[j][k] = cj * sc + cs;
        M[k][k] = cj * cc - ss;
    }
    else
    {
        M[i][i] = cj * ch;
        M[j][i] = sj * sc - cs;
        M[k][i] = sj * cc + ss;
        M[i][j] = cj * sh;
        M[j][j] = sj * ss + cc;
        M[k][j] = sj * cs - sc;
        M[i][k] = -sj;
        M[j][k] = cj * si;
        M[k][k] = cj * ci;
    }

    return M;
}

template <class T>
IMATH_HOSTDEVICE Matrix44<T>
Euler<T>::toMatrix44() const IMATH_NOEXCEPT
{
    int i, j, k;
    angleOrder (i, j, k);

    Vec3<T> angles;

    if (_frameStatic)
        angles = (*this);
    else
        angles = Vec3<T> (z, y, x);

    if (!_parityEven)
        angles *= -1.0;

    T ci = std::cos (angles.x);
    T cj = std::cos (angles.y);
    T ch = std::cos (angles.z);
    T si = std::sin (angles.x);
    T sj = std::sin (angles.y);
    T sh = std::sin (angles.z);

    T cc = ci * ch;
    T cs = ci * sh;
    T sc = si * ch;
    T ss = si * sh;

    Matrix44<T> M;

    if (_initialRepeated)
    {
        M[i][i] = cj;
        M[j][i] = sj * si;
        M[k][i] = sj * ci;
        M[i][j] = sj * sh;
        M[j][j] = -cj * ss + cc;
        M[k][j] = -cj * cs - sc;
        M[i][k] = -sj * ch;
        M[j][k] = cj * sc + cs;
        M[k][k] = cj * cc - ss;
    }
    else
    {
        M[i][i] = cj * ch;
        M[j][i] = sj * sc - cs;
        M[k][i] = sj * cc + ss;
        M[i][j] = cj * sh;
        M[j][j] = sj * ss + cc;
        M[k][j] = sj * cs - sc;
        M[i][k] = -sj;
        M[j][k] = cj * si;
        M[k][k] = cj * ci;
    }

    return M;
}

template <class T>
IMATH_HOSTDEVICE Quat<T>
Euler<T>::toQuat() const IMATH_NOEXCEPT
{
    Vec3<T> angles;
    int i, j, k;
    angleOrder (i, j, k);

    if (_frameStatic)
        angles = (*this);
    else
        angles = Vec3<T> (z, y, x);

    if (!_parityEven)
        angles.y = -angles.y;

    T ti = angles.x * 0.5;
    T tj = angles.y * 0.5;
    T th = angles.z * 0.5;
    T ci = std::cos (ti);
    T cj = std::cos (tj);
    T ch = std::cos (th);
    T si = std::sin (ti);
    T sj = std::sin (tj);
    T sh = std::sin (th);
    T cc = ci * ch;
    T cs = ci * sh;
    T sc = si * ch;
    T ss = si * sh;

    T parity = _parityEven ? 1.0 : -1.0;

    Quat<T> q;
    Vec3<T> a;

    if (_initialRepeated)
    {
        a[i]     = cj * (cs + sc);
        a[j]     = sj * (cc + ss) * parity, // NOSONAR - suppress SonarCloud bug report.
            a[k] = sj * (cs - sc);
        q.r      = cj * (cc - ss);
    }
    else
    {
        a[i]     = cj * sc - sj * cs,
        a[j]     = (cj * ss + sj * cc) * parity, // NOSONAR - suppress SonarCloud bug report.
            a[k] = cj * cs - sj * sc;
        q.r      = cj * cc + sj * ss;
    }

    q.v = a;

    return q;
}

template <class T>
IMATH_HOSTDEVICE constexpr inline bool
Euler<T>::legal (typename Euler<T>::Order order) IMATH_NOEXCEPT
{
    return (order & ~Legal) ? false : true;
}

template <class T>
IMATH_HOSTDEVICE IMATH_CONSTEXPR14 typename Euler<T>::Order
Euler<T>::order() const IMATH_NOEXCEPT
{
    int foo = (_initialAxis == Z ? 0x2000 : (_initialAxis == Y ? 0x1000 : 0));

    if (_parityEven)
        foo |= 0x0100;
    if (_initialRepeated)
        foo |= 0x0010;
    if (_frameStatic)
        foo++;

    return (Order) foo;
}

template <class T>
IMATH_HOSTDEVICE inline void
Euler<T>::setOrder (typename Euler<T>::Order p) IMATH_NOEXCEPT
{
    set (p & 0x2000 ? Z : (p & 0x1000 ? Y : X), // initial axis
         !(p & 0x1),                            // static?
         !!(p & 0x100),                         // permutation even?
         !!(p & 0x10));                         // initial repeats?
}

template <class T>
IMATH_HOSTDEVICE inline void
Euler<T>::set (typename Euler<T>::Axis axis, bool relative, bool parityEven, bool firstRepeats) IMATH_NOEXCEPT
{
    _initialAxis     = axis;
    _frameStatic     = !relative;
    _parityEven      = parityEven;
    _initialRepeated = firstRepeats;
}

template <class T>
IMATH_HOSTDEVICE IMATH_CONSTEXPR14 inline const Euler<T>&
Euler<T>::operator= (const Euler<T>& euler) IMATH_NOEXCEPT
{
    x                = euler.x;
    y                = euler.y;
    z                = euler.z;
    _initialAxis     = euler._initialAxis;
    _frameStatic     = euler._frameStatic;
    _parityEven      = euler._parityEven;
    _initialRepeated = euler._initialRepeated;
    return *this;
}

template <class T>
IMATH_HOSTDEVICE IMATH_CONSTEXPR14 inline const Euler<T>&
Euler<T>::operator= (const Vec3<T>& v) IMATH_NOEXCEPT
{
    x = v.x;
    y = v.y;
    z = v.z;
    return *this;
}

template <class T>
IMATH_HOSTDEVICE IMATH_CONSTEXPR14 inline float
Euler<T>::angleMod (T angle) IMATH_NOEXCEPT
{
    const T pi = static_cast<T> (M_PI);
    angle      = fmod (T (angle), T (2 * pi));

    if (angle < -pi)
        angle += 2 * pi;
    if (angle > +pi)
        angle -= 2 * pi;

    return angle;
}

template <class T>
IMATH_HOSTDEVICE inline void
Euler<T>::simpleXYZRotation (Vec3<T>& xyzRot, const Vec3<T>& targetXyzRot) IMATH_NOEXCEPT
{
    Vec3<T> d = xyzRot - targetXyzRot;
    xyzRot[0] = targetXyzRot[0] + angleMod (d[0]);
    xyzRot[1] = targetXyzRot[1] + angleMod (d[1]);
    xyzRot[2] = targetXyzRot[2] + angleMod (d[2]);
}

template <class T>
IMATH_HOSTDEVICE void
Euler<T>::nearestRotation (Vec3<T>& xyzRot, const Vec3<T>& targetXyzRot, Order order) IMATH_NOEXCEPT
{
    int i, j, k;
    Euler<T> e (0, 0, 0, order);
    e.angleOrder (i, j, k);

    simpleXYZRotation (xyzRot, targetXyzRot);

    Vec3<T> otherXyzRot;
    otherXyzRot[i] = M_PI + xyzRot[i];
    otherXyzRot[j] = M_PI - xyzRot[j];
    otherXyzRot[k] = M_PI + xyzRot[k];

    simpleXYZRotation (otherXyzRot, targetXyzRot);

    Vec3<T> d  = xyzRot - targetXyzRot;
    Vec3<T> od = otherXyzRot - targetXyzRot;
    T dMag     = d.dot (d);
    T odMag    = od.dot (od);

    if (odMag < dMag)
    {
        xyzRot = otherXyzRot;
    }
}

template <class T>
IMATH_HOSTDEVICE void
Euler<T>::makeNear (const Euler<T>& target) IMATH_NOEXCEPT
{
    Vec3<T> xyzRot = toXYZVector();
    Vec3<T> targetXyz;
    if (order() != target.order())
    {
        Euler<T> targetSameOrder = Euler<T> (target, order());
        targetXyz                = targetSameOrder.toXYZVector();
    }
    else
    {
        targetXyz = target.toXYZVector();
    }

    nearestRotation (xyzRot, targetXyz, order());

    setXYZVector (xyzRot);
}

/// @endcond

/// Stream ouput, as "(x y z i j k)"
template <class T>
std::ostream&
operator<< (std::ostream& o, const Euler<T>& euler)
{
    char a[3] = { 'X', 'Y', 'Z' };

    const char* r = euler.frameStatic() ? "" : "r";
    int i, j, k;
    euler.angleOrder (i, j, k);

    if (euler.initialRepeated())
        k = i;

    return o << "(" << euler.x << " " << euler.y << " " << euler.z << " " << a[i] << a[j] << a[k]
             << r << ")";
}

#if (defined _WIN32 || defined _WIN64) && defined _MSC_VER
#    pragma warning(pop)
#endif


IMATH_INTERNAL_NAMESPACE_HEADER_EXIT

#endif // INCLUDED_IMATHEULER_H