Quote: "How can a cube be inside out?
Am I right in thinking that each vertex has its own normal"
When looking at the cube you won't see the outside faces - you will see the three inside backfaces so it will look as though there are no sides towards the camera. It will appear to recess. It's hard to describe but you'll see it if you look for it.
A normal is calculated using vectors. Since a vertex is a point, it can't have a normal. However, for lighting effects and smoother gradation, an average of the face normals surrounding a vertex are taken and this average vector is often called the vertex normal. In a directx file, the normals are usually represented as averaged face normals and called vertex normals.
As far as displaying the polygon, the crossproduct of the actual vertices is taken to produce a face normal (seems redundant doesn't it?). The reason is a face normal is needed in order to be able to display the polygon. The vertex normals are used to control the lighting. I haven't downloaded your example so I don't know if this has naything to do with your problem.
Anyway, here's a clearer example of what I was talking about. I'm attaching a grid that has normals on only the front side. If you rotate this grid around x (basically flip it over) it will disappear once the backside is exposed to the camera.
Enjoy your day.
