How to get the interpolated vectors/quaternions between keyframe positions?

It looks like Threejs has the interpolation functions somewhere but I wonder if there is any public API which can show these interpolated data (vectors/quaternions) since my app needs those values during the animation.
Many thanks.

You always interpolate object properties (e.g. Object3D.position or Object3D.quaternion) with the animation system. By accessing the animated properties per frame/animation step, you automatically have the so called inbetweens. The animated data between keyframes.

Thank you for the answer.

My problem to solve is to divide the animation into of a given number of steps, for which in each step, user can see beforehand the changes of distance and angulation. Moreover, user can use the slider to go forward to a specific step.

I walked around by using vector3.lerp and quaternion.slerp to have these numbers but it wasn’t a clean code since the object is a child.

Also, I still have no idea of how to stop the animation in each specific step.

Here is the proposed interface.

displacements