internal DrawCommands( World _world, Commands commands ) {
world = _world;
commands.AddCommand( "cuboid", Cuboid, true );
commands.AddCommand( "cub", Cuboid, true );
commands.AddCommand( "ellipsoid", Ellipsoid, true );
commands.AddCommand( "ell", Ellipsoid, true );
commands.AddCommand( "mark", Mark, true );
commands.AddCommand( "undo", UndoDraw, true );
commands.AddCommand( "cancel", CancelDraw, true );
}