It is well known that in rigid body, there are 2 ways to representing rotations in 3D: Euler and Quaternion. Empirically, has been noted that both methods have advantages (In Euler there's not redundancy and Quaternions there are stable interpolations of possible rotations) and disadvantages (In Euler exists the gimbal lock singularity and Quaternions there are redundancy by using 4 values to represent the DOF or degrees of freedom). Nevertheless, i've not found a technical and measurement report about when is recommended use Quaternions vs Euler representation, e.g. (recording a complex sport gesture, or recording a simple movement gesture). Even, in the ISB (international society of biomechanics) recommendations on definitions of joint coordinate system of joints for human analysis, there's no given an explanation of using an Euler representation in human motion.
Thanks
I'm using quaternions, but it does not help in answering your question. So, please, let me intriduce you with Dr. Chris Kirtley who asked the very same question than yours 15 years ago (http://biomch-l.isbweb.org/threads/11415-Summary-Quaternions-vs-Euler-angles). He said : "I guess it's time I summarized the great quaternion debate. To remind you, I asked why quaternions (otherwise known as Euler parameters) seem to be used as the standard method for representaing motion in computer animation and video games, but are not so often used in biomechanics. It seems that, whilst quaternions have advantages in terms of lack of gymbal lock, and insensitivity to round-off errors, they suffer from problems of interpretation in terms of meaningfully clinical or anatomical angles. As Joe Sommer and Bruce MacWilliams suggest, the best compromise is perhaps to use quaternions for intermediate calculations, then convert to Euler angles at the end." I do share their advice; using quaternions for math, and convert to Euler at the end to help our 3D-limited brain.
Hello there
"Even, in the ISB (international society of biomechanics) recommendations on definitions of joint coordinate system of joints for human analysis, there's no given an explanation of using an Euler representation in human motion."
I am not agree with you at this statement. ISB recommendation is only for joint coordinate definition. Therefore, there is no explanation of motion using Euler angle or Quaternion method. However, ISB recommendation stated as "All recommendation of JCS for various joints follow the similar procedures as proposed by Grood and Suntay 1983." which means that motion representation is similar to that in Grood and Suntay 1983.
If you check article by Grood and Suntay, there is clear mathematical expression of knee joint clinical motion using Euler angles.
Best: Purevsuren
Hello Mario Casanova ,
Did you find a good comparison between Euler angles vs Quaternions in human motion analysis? Could you please be kind enough to share it with me.
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