Rodrigo: Good to hear that it's working!

Raph: Like Wim said, quaternions are tough to get right, and it's best
to use the implementation of an existing library.

That said, if you'd like a very in-depth explanation of quaternions
have a look at this paper:

http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.30.6788

-Stu

On Mon, Jan 10, 2011 at 9:05 AM, Wim Meeussen <meeussen@willowgarage.com> wrote:
> Raph,
>
>
>> I am also fighting hard to grasp the concepts of quaternions.
>> Could you explain how to get back the Pich, Roll and Yaw values from a
>> quaternion?
>> I understand I should come back to the axis-angle representation, but how to
>> extract the roll value in radians for example?
>
> Wikipedia is a good reference:
> <http://en.wikipedia.org/wiki/Conversion_between_quaternions_and_Euler_angles>
>
> You also don't have to implement these conversions yourself, there are
> a number of great libraries around that can have well tested
> implementations. The KDL library is a good example.
> <http://www.orocos.org/kdl/geometry>
>
> Hope this helps,
>
> Wim
>
>
>
>
> --
> --
> Wim Meeussen
> Willow Garage Inc.
> <http://www.willowgarage.com)
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>



-- 
Stuart Glaser
sglaser -at- willowgarage -dot- com
www.willowgarage.com