Surface from section

 

One method of creating a terrain model is to place a (theoretical) cross-section along an axis:

When running the wizard, you are asked to select a 2D polyline representing the cross-section:

After that you are asked to choose a point on this line where it will be placed along the axis line.

Next an axis line is asked to be selected. An arrow indicates the direction along which the cross-sections will be placed, so pay attention to the correct direction:

If a 3D polyline is selected, the elevation of that polyline will be taken over. When a 2D polyline is selected, you are asked to enter the elevation of the selected point on the cross-section, or to enter a reference point.

Het final result is a Civil 3D Surface: