OVITO Forum
OVITO => Support Forum => Topic started by: lx_pico on June 04, 2019, 10:16:12 AM

Hi, Alex and OVITO users,
I don't understand how the quaternion R(X, Y, Z, W) in atomic strain modifiers is obtained from the rotation matrix, specifically, what are the physical meanings of the value of Rotation.XW respectively? can you guys give me some imformation?
Thanks.
Peter

Hello Peter,
this might be helpful
https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation (https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation)
and also the link to the OVITO code if you're interested in the technical details:
https://gitlab.com/stuko/ovito/blob/master/src/core/utilities/linalg/Quaternion.h#L283318 (https://gitlab.com/stuko/ovito/blob/master/src/core/utilities/linalg/Quaternion.h#L283318)
Constanze

Thank you, Constanze.
Now I understand that Rotation.i = ui*sin(theta/2), where theta is the rotation angle and ui the ith component of unit rotation axis, and Rotation.W = cos(theta/2).