public static Spatial createSky(AssetManager assetManager,
            Texture west, Texture east, Texture north, Texture south, Texture up, Texture down) {
        return createSky(assetManager, west, east, north, south, up, down, Vector3f.UNIT_XYZ);
    }
Create a cube-mapped sky using six textures.

@param assetManager from which to load materials
@param west texture for the western face of the cube
@param east texture for the eastern face of the cube
@param north texture for the northern face of the cube
@param south texture for the southern face of the cube
@param up texture for the top face of the cube
@param down texture for the bottom face of the cube
@return a new spatial representing the sky, ready to be attached to the
scene graph
jme3-core/src/main/java/com/jme3/util/SkyFactory.java