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It is weird question, but from what I read in one software documentation it states:

"With respect to rotations, the constraint is different along different local directions. Along the z-axis (twist direction), the constraint is identical to the one enforced via the continuum coupling method (see Distributing coupling constraints). By contrast, the rotational constraint in the plane perpendicular to the z-axis relates the in-plane reference node rotations to the in-plane rotations of the coupling nodes in the immediate vicinity of the reference node. This choice provides a more realistic (compliant) response when the constrained surface is small and deforms primarily in a bending mode."

By rotation vector, I meant rotation axis-angle vector, pseduo-vector. My understanding of how rotation pseudo-vector being updated is that I have two rotation pseudo-vectors $\textbf{v}(v_1,v_2,v_3)$ and $\textbf{u}(u_1,u_2,u_3)$, and by the rule it states, the rotation pseudo-vector by adding them is $\textbf{w}=(u_1,u_2,v_3)$, is it correct rotation updates?

Hankang Yang
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  • There are two main methods for rotating vectors: rotation matrices and quaternions. Both involve non-commutative multiplications. I'm not sure why you're talking about rotation vectors. What is the interpretation of your rotation vectors? Rotating a vector is an operation that requires a matrix or quaternion multiplication. Naturally, you can add two vectors together, but you should be aware of what the interpretation of the result is. – Adrian Keister Sep 28 '21 at 17:53
  • Are your rotation vectors some Euler Angles? I'm not sure how else to interpret a rotation vector in $\mathbb{R}^3$ – Brian Lai Sep 28 '21 at 17:55
  • by rotation vector, I meant rotation axis-angle vector, aka pseudo-vector. Changed the description – Hankang Yang Sep 28 '21 at 18:56
  • The quoted text does not say anything about adding "rotation vectors". How did you arrive at that conclusion? – Tpofofn Sep 29 '21 at 00:43
  • @Tpofofn, it is exactly what I am asking. Whether my understanding is correct? or what the correct one? – Hankang Yang Sep 30 '21 at 01:17

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