AxisAngle class describing rotation represented with direction axis (3D Vector) and an
angle of rotation around that axis.
@ingroup GenVector
| static double | Pi() |
| void | RectifyAngle() |

Construct from a non-zero vector (x,y,z) and an angle.
Precondition: the Vector needs to implement x(), y(), z(), and unit()
{ }
Construct given a pair of pointers or iterators defining the
beginning and end of an array of four Scalars, to be treated as
the x, y, and z components of a unit axis vector, and the angle
of rotation.
Precondition: The first three components are assumed to represent
the rotation axis vector and the 4-th the rotation angle.
The angle is assumed to be in the range (-pi,pi].
The axis vector is automatically normalized to be a unit vector
{ SetComponents(begin,end); } The compiler-generated copy ctor, copy assignment, and dtor are OK.
Re-adjust components to eliminate small deviations from the axis
being a unit vector and angles out of the canonical range (-pi,pi]
======== Construction From other Rotation Forms ==================
Construct from another supported rotation type (see gv_detail::convert )
{gv_detail::convert(r,*this);}
Assign from another supported rotation type (see gv_detail::convert )
======== Components ==============
Set the axis and then the angle given a pair of pointers or iterators
defining the beginning and end of an array of four Scalars.
Precondition: The first three components are assumed to represent
the rotation axis vector and the 4-th the rotation angle.
The angle is assumed to be in the range (-pi,pi].
The axis vector is automatically normalized to be a unit vector
Get the axis and then the angle into data specified by an iterator begin
and another to the end of the desired data (4 past start).
Multiplication of an axial rotation by an AxisAngle