3d model import problem.

Hi , I am pretty new to 3d modeling and unity and I have a problem with my model.
I try to create a tunnel using NURBS Circle Surfaces in blender. It looks ok in Blender but when I import it to Unity I see completely different thing. Please take a look on the screenshots attached. I have huge experience in software development but pretty lame in 3D modeling :-(.


P.S I am using unity 3.5.6f4 and Blender 2.6

 

This is kind of like a theory lesson:
In 3d models you have faces these have things called normals on them normals can only be shown in one direction the direction they are facing is outwards on your model. in blender you see the object as though it was real but is you textured it and viewed it in textured mode it be the same as it appears in unity. If you want the player to be able to see inside the object you need to have face on the inside too with normals facing inwards other wise its just invisible.

To fix the problem you will have to bring the shape in on its self so it has a inside and outside think of a coffee cup the way it has thick walls it goes back in and done its basically the same concept.

Unfortunately its hard to explain there inst really many resources out there you kind of just figure it out by mistake.

 

you will need a double sided shader for this kind. to avoid some issues in later models,make sure that faces normals are facing outside.
http://answers.unity3d.com/questions/8624/double-sided-plane-with-texture.html

 

Thanks your answers were helpful hope I will be able to make something useable now ;-)