## Quaternion between two quaternions [closed]

Hello, I have an orientation P1 in a 3D space, represented as a quaternion [w x y z]. Then P1 is rotated using another quaternion (q1) with the formula

P2=q1*P1*q1'

Is there any formula in order to get q1 from P2 and P1?

Thank you.

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 What is an "orientation"? – Igor Rivin Apr 15 2011 at 15:20