How does the rotation work in Object3D (for HumanoidBone node)?

Questions
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I’m really new to three.js and animation in general, so apologies if the question doesn’t make sense here.

So I have a sequence of frames, where for each frame I have a 3D coordinates of a single human body (e.g. left eye, right eye, left shoulder etc). I’d like to have an animated character to move based on the coordinates provided.

Seem like we i need to do is to compute and assign the rotation attribute to the Object3D (which is returned from currentVrm.humanoid.getBoneNode) and on the doc it says it’s euler angles. After some readings on euler angles, they are a sequence of angles that you apply one after the other (so subsequent rotations is based on the previous frame) to get to a certain position. But what im really confused about is,

  1. the rotation attribute has x, y, z instead of theta, phi, psi e.g. are they the euler angle as how i understood?
  2. if so, i only have the coordinates (i suppose in the base three.js frame i.e. y points up, x points to right of screen and z comes out of screen) for human body parts e.g. left eye and right eye, etc, how can i compute the euler angle and assign it to the Object3D?
  3. if not, what exactly are them then? are they simply the angle between the vector (e.g. left eye=(1.5, 2, 0.4)) and the x, y and z axis?

thanks!