In 3ds max, when creating an spline using arcs, why isn't it solid when using the extrude mod? i'm using 3ds max, and attempting to create an spline using an intial arc , resizing the arc to create an inner arc, then attaching two horizontal lines to create a rainbow in a sense....when extruding it it is not solid, yet when creating a closed spline it always is solid....I'm confused as how to close the spline as well...