three.js/src/textures/CubeTexture.js

/**
 * @author mrdoob / http://mrdoob.com/
 */

THREE.CubeTexture = function ( images, mapping, wrapS, wrapT, magFilter, minFilter, format, type, anisotropy ) {

	mapping = mapping !== undefined ? mapping : THREE.CubeReflectionMapping;
	
	THREE.Texture.call( this, images, mapping, wrapS, wrapT, magFilter, minFilter, format, type, anisotropy );

	this.images = images;

};

THREE.CubeTexture.prototype = Object.create( THREE.Texture.prototype );
THREE.CubeTexture.prototype.constructor = THREE.CubeTexture;

THREE.CubeTexture.clone = function ( texture ) {

	if ( texture === undefined ) texture = new THREE.CubeTexture();

	THREE.Texture.prototype.clone.call( this, texture );

	texture.images = this.images;

	return texture;

};