Angles computation

[Carlo Tricarico]

Hi everybody,
I've got a question dealing with the computation of angles during the Inverse Kinematics tool: angles between the various bony segments are considered according to which convention? Euler or Cardan?

Thank you in advance for your answers

[jimmy d]

Hi Carlo,

Angles can be considered according to any definition you would like. A brief description can be found here ;
http://simtk-confluence.stanford.edu:80 ... odeling-A2 Definejointsbetweenbodiesgroundandtwohalves

"In our case, we do so because we want to specify the type of Euler angles that describe the orientation of the cat's anterior segment. Although the FreeJoint also uses Euler angles, it does not allow the modeler to choose which type of Euler angles are used.

We choose YZX Euler angles, named yaw, pitch, and roll respectively, to avoid representation singularities. We specify this via a SpatialTransform object, which we'll use to define our CustomJoint. A spatial transform has 6 transform axes. The first 3 are rotations, defined about the axes of our choosing. The remaining 3 are translations, for which we can also set the axes. We choose the translation axes to be the X, Y, and Z directions of the ground's frame, which are also the default (XYZ, not YZX, Euler angles are the default)."

hope that helps,
-james

[Carlo Tricarico]

Hi James,
thanks a lot for your precise replay, it has been useful.

Best regards

Carlo