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

		const times = [ 0, period ], values = [ 0, 1 ];

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

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

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

	}
Creates an animation clip that scales a 3D object from `0` to `1`
in the given period of time along the given axis.

@param {number} period - The duration of the animation.
@param {('x'|'y'|'z')} [axis='x'] - The axis to scale the 3D object along.
@return {AnimationClip} The created animation clip.