quaternion norm

[Ben P]

I am tracking rotation of an object using quaternions by accumulating each successive rotation using quaternion composition.

I notice that probably due to rounding errors, the norm of each successive quaternion is drifting from being 1, which means I need to normalize the quaternion.

Is there an in-build function that would let me do this? 

Otherwise, I can divide the quaternion by its norm. Is there a method I can call on the quaternion to extract its norm?

I looked at the Quaternion documentation page but did not find anything there Here is the page I am referring to: http://doc.sagemath.org/html/en/reference/quat_algebras/sage/algebras/quatalg/quaternion_algebra.html

Thanks

Ben

[Dima Pasechnik]

On Tuesday, 16 June 2015 23:54:14 UTC+1, Ben P wrote:

I am tracking rotation of an object using quaternions by accumulating each successive rotation using quaternion composition.

I notice that probably due to rounding errors, the norm of each successive quaternion is drifting from being 1, which means I need to normalize the quaternion.

Is there an in-build function that would let me do this? 

Otherwise, I can divide the quaternion by its norm. Is there a method I can call on the quaternion to extract its norm?

for r an element of your quaternion algebra Q, you can do something like

 vector(r.coefficient_tuple())*Q.inner_product_matrix()* vector(r.coefficient_tuple())

to get some kind of norm (probably you'd need to scale it)