How do you convert a quaternion into an axis-angle representation?

asked 2012-09-20 13:13:05 -0500

derekjchow
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updated 2012-09-20 17:06:52 -0500

joq
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Hello,

I'd like to convert an orientation from geometry_msgs::Quaternion to an axis-angle representation (http://en.wikipedia.org/wiki/Axis-angle_representation). Similarly, I'd like to convert back to a quaternion from an axis-angle value. What ROS libraries are available to preform these conversions?

Thanks

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I answered this question, then edited that and it disappeared. It does not allow me to answer again! The best I could do: https://gist.github.com/e5170cf046b8001f4e65

Mani ( 2012-09-20 15:00:51 -0500 )edit

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answered 2012-09-20 17:43:49 -0500

jbohren

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updated 2012-09-20 17:46:18 -0500

TF datatypes are actually re-cast Bullet Datatypes. If you have a tf::Quaternion, you can use any of the functions dejan linked to above, but specifically, you want these two:

double btQuaternion::GetAngle()

btVector3 btQuaternion::GetAxis()

When you want to change the value of a tf::Quaternion from an axis/angle representation, you can use this member function:

void btQuaternion::SetRotation(const btVector3 &axis, const double &angle)