loadCubemap( urls, onLoad, onProgress, onError ) {

		const texture = new CubeTexture();

		for ( let i = 0; i < 6; i ++ ) {

			texture.images[ i ] = undefined;

		}

		let loaded = 0;

		const scope = this;

		function loadTexture( i ) {

			scope.load( urls[ i ], function ( image ) {

				texture.images[ i ] = image;

				loaded ++;

				if ( loaded === 6 ) {

					texture.needsUpdate = true;

					if ( onLoad ) onLoad( texture );

				}

			}, undefined, onError );

		}

		for ( let i = 0; i < urls.length; ++ i ) {

			loadTexture( i );

		}

		texture.type = this.type;
		texture.format = RGBAFormat;
		texture.minFilter = LinearFilter;
		texture.generateMipmaps = false;

		return texture;

	}
Starts loading from the given URLs and passes the loaded RGBM cube map
to the `onLoad()` callback.

@param {Array<string>} urls - The paths/URLs of the files to be loaded. This can also be a data URIs.
@param {function(CubeTexture)} onLoad - Executed when the loading process has been finished.
@param {onProgressCallback} onProgress - Executed while the loading is in progress.
@param {onErrorCallback} onError - Executed when errors occur.
@return {CubeTexture} The cube texture.