How do you get the local angular velocity of a Spatial Node?

joeyq

I want to brush up on learning to work with 3d stuff like acceleration, velocities, matrices etc. here's an example code:

func _process(_delta):
	## get global angular rotation.
	v_a_glob = (self.rotation - r_prev) /_delta
	r_prev = self.rotation
	## get local angular rotation.
	#v_a_loc = self.to_local(v_a_glob)
	v_a_loc = self.transform.basis.xform_inv(v_a_glob)

when the spatial node is unrotated it works, but if I rotate it in an arbitrary way it doesn't work anymore here's the example project w and s move the node forward and backward locally, a and d rotate locally on the y axis (jaw)

joeyq

I made a mistake in thinking that you could get the global angular velocity by just subtracting the current rotation from the previous rotation. I search further on the internet and found user balintmaci who put this code for getting (global) angular velocity. https://github.com/godotengine/godot-proposals/issues/3626 Angular velocity is difficult to calculate when throwing rigid bodies in VR games #3626

func calculate_angular_velocity(orientation_new: Basis, orientation_old: Basis, time_new: int, time_old: int):
    var time_elapsed = (time_new - time_old) / 1000000.0 # convert microseconds to seconds
    var orientation_new_relative_to_old = orientation_old.inverse() * orientation_new
    var axis_angle_new_relative_to_old = quat2axis_angle(Quat(orientation_new_relative_to_old))
    var angular_velocity_in_relative_frame = axis_angle_new_relative_to_old / time_elapsed
    return orientation_old * angular_velocity_in_relative_frame # axis transformed back to global frame, but retains magnitude

static func quat2axis_angle(q: Quat):
    var v = Vector3(q.x, q.y, q.z)
    var angle = 2 * atan2(v.length(), q.w)
    return v.normalized() * angle

I edited it a little in my test project and it worked, yay!