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[Jan Stránský <question692057@xxxxxxxxxxxxxxxxxxxxx>]

Question #692057 on Yade changed:
https://answers.launchpad.net/yade/+question/692057

    Status: Open => Answered

Jan Stránský proposed the following answer:
Hello,

1.
the quaternion is printed in its axis-angle representation. The orientation is represented as "rotation by the angle around the axis"

2.
Using "utils" particle creation method (e.g. utils.sphere, utils.box, ...), which I suppose, state.refOri is set as the initial value of state.ori

refOri does not change "automatically", but you can change it "manually"
if you like.

3.
see the source code [1]. it is angle equivalent of state.displ() [2], i.e. rotation "between" state.refOri and state.ori.
The vector i axis*angle
However, there is a problem for "large rotations", e.g. rolling of particles. Have a look at similar discussion [3] (from comment #14 on) if this your case

4.
yes. This is actually what state.displ() [2] does

cheers
Jan

[1] https://gitlab.com/yade-dev/trunk/-/blob/master/core/State.hpp#L40
[2] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.State.displ
[3] https://answers.launchpad.net/yade/+question/688763

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