Quaternion usage

[nizar sallem]

Hi,

I was wondering what is the equivalent to this cpp call
Eigen::Quaternionf q_1 (Eigen::AngleAxisf(M_PI/3, Eigen::Vector3f::UnitZ()));
I was assuming it is
q1 = Quaternion((0,0,1),math.pi/3)
but the results don't look the same:
std::cout << q_1.w() << " " << q_1.x() << " " << q_1.y() << " " << q_1.z() << std::endl;
returns
0.92388 0 0 0.382683
while
print q1
returns
Quaternion((0,0,1),0.7853981633974484)

Is there a way to get this a quaternion from a unit vector and an angle in minieigen ?

[Václav Šmilauer (eudoxos)]

Hi,

I did not see the bug for some reason (no notification from LP?).

It is not really a but, minieigen always prints Quaternion as axis-angle. Quaternion((0,0,1),0.7853981633974484) is how you construct it (Quaternion((0,0,1),math.pi/3)).

If you want to obtain (or set) the coefficients which are internally stored, use index notation, q[0] for q.x(), q[1] for q.y(), q[2] for q.z() and q[3] for q.w().

HTH, Václav

[Václav Šmilauer (eudoxos)]

PS The development really happens over at http://github.com/eudoxos/minieigen, not here anymore.

[Václav Šmilauer (eudoxos)]

Closing, hopefully resolved.

[nizar sallem (nizar-sallem)]

Thanks

On Sat, Oct 24, 2015 at 3:41 AM, Václav Šmilauer <email address hidden> wrote:

> Closing, hopefully resolved.
>
> ** Changed in: minieigen
> Status: New => Fix Released
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1474244
>
> Title:
> Quaternion usage
>
> Status in minieigen:
> Fix Released
>
> Bug description:
> Hi,
>
> I was wondering what is the equivalent to this cpp call
> Eigen::Quaternionf q_1 (Eigen::AngleAxisf(M_PI/3,
> Eigen::Vector3f::UnitZ()));
> I was assuming it is
> q1 = Quaternion((0,0,1),math.pi/3)
> but the results don't look the same:
> std::cout << q_1.w() << " " << q_1.x() << " " << q_1.y() << " " <<
> q_1.z() << std::endl;
> returns
> 0.92388 0 0 0.382683
> while
> print q1
> returns
> Quaternion((0,0,1),0.7853981633974484)
>
> Is there a way to get this a quaternion from a unit vector and an
> angle in minieigen ?
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/minieigen/+bug/1474244/+subscriptions
>