static CreateRotationAnimation( period, axis = 'x' ) {

		const times = [ 0, period ], values = [ 0, 360 ];

		const trackName = '.rotation[' + axis + ']';

		const track = new NumberKeyframeTrack( trackName, times, values );

		return new AnimationClip( '', period, [ track ] );

	}
Creates an animation clip that rotates a 3D object 360 degrees
in the given period of time around the given axis.

@param {number} period - The duration of the animation.
@param {('x'|'y'|'z')} [axis='x'] - The axis of rotation.
@return {AnimationClip} The created animation clip.