+ // add a cloud layer (above sea level in meters)
+ void add_cloud_layer( double asl, double thickness,
+ double transition, double span,
+ SGCloudType type );
+ void add_cloud_layer( double asl, double thickness,
+ double transition, double span,
+ const string &tex_path );
+ void add_cloud_layer( double asl, double thickness,
+ double transition, double span,
+ ssgSimpleState *state );