createNormalizedNormalAttribute( normal ) {

		const cache = this.cache;

		if ( cache.attributesNormalized.has( normal ) )	return cache.attributesNormalized.get( normal );

		const attribute = normal.clone();
		const v = new Vector3();

		for ( let i = 0, il = attribute.count; i < il; i ++ ) {

			v.fromBufferAttribute( attribute, i );

			if ( v.x === 0 && v.y === 0 && v.z === 0 ) {

				// if values can't be normalized set (1, 0, 0)
				v.setX( 1.0 );

			} else {

				v.normalize();

			}

			attribute.setXYZ( i, v.x, v.y, v.z );

		}

		cache.attributesNormalized.set( normal, attribute );

		return attribute;

	}
Creates normalized normal buffer attribute.

@param {BufferAttribute} normal
@returns {BufferAttribute}