This is the dialog where you specify the tunnel perimeter.

First, you must specify the name and the chainage interval for the perimeter. The name is just for making it easy to recognize the perimeter specification.

A perimeter can be specified as either

A perimeter defines as a parametric cross-section that has the same parameters as the general parametric inner profile. You can specify which road surface edge lines to connect to. The perimeter will always have the same rotation as the inner profile.

The perimeter is connected to the theoretical base to form a closed polygon. If you in addition to the theoretical base have defined a design base, the perimeter will connect to both base definitions. The perimeter area given at the status bar in the Define Tunnel Profile Geometry dialog is always calculated based on the theoretical base.

Next topic: 3D Triangulation