You've built things in a similar way to how I would model that sort of shape. I think you've just hit upon a weakness in VW - it doesn't do large curves well. I've had this problem a lot with larger curved objects. I believe its directly related to how VW breaks curves down into segments for rendering. If the object is small, there's enough segments and it looks ok. As the curve gets larger, the segments get larger and it begins to look awful. Even when you turn the various conversion resolution