public static Spatial createSky(AssetManager assetManager, Texture texture,
            Vector3f normalScale, EnvMapType envMapType) {
        return createSky(assetManager, texture, normalScale, envMapType, 10);
    }
Create a sky with radius=10 using the given cubemap or spheremap texture.

For the sky to be visible, its radius must fall between the near and far
planes of the camera's frustum.

@param assetManager from which to load materials
@param texture to use
@param normalScale The normal scale is multiplied by the 3D normal to get
a texture coordinate. Use Vector3f.UNIT_XYZ to not apply and
transformation to the normal.
@param envMapType see {@link EnvMapType}
@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