Dear Nick,

Thank you for your efforts. I need the roughness of the tunnel in my simulation. That's why I was using a LiDAR scan model in my simulation and trying to reduce it to 1 meter to reduce the computational resources finally see the screenshot with 1m by 1m of the tunnel section. 

When I tried to do what you shared, I am not getting the same options as you, i.e., inside, and outside, and could not thicken its walls as you can see in the screenshot. Kindly guide.