If you are running AutoCAD Civil 3D 2017 on a supported platform, a corridor tab is available. This defines how the 3D model of the roundabout is built and updated.
Click Corridor in the left hand pane. The Corridor page is displayed.
The checkboxes in the upper section of the page control how much of the 3D model AutoCAD Civil 3D 2017 creates and updates.
Select Create Alignments to create horizontal alignments in your CAD system.
Select Update Alignments if you want AutoCAD Civil 3D 2017 to update the alignments automatically when the geometry changes. This option is only available if AutoCAD Civil 3D 2017 created the original alignments, i.e. if Create Alignments is selected
Select Create Profiles to create vertical profiles along the horizontal alignments.
Select Update Profiles if you want AutoCAD Civil 3D 2017 to update the profiles automatically when the geometry changes. This option is only available if AutoCAD Civil 3D 2017 created the original profiles, i.e. if Create Profiles is selected
Select Create Corridor to create a 3D corridor model using default assemblies.
Select Update Corridor if you want AutoCAD Civil 3D 2017 to update the corridor automatically when the geometry changes. This option is only available if AutoCAD Civil 3D 2017 created the original corridor, i.e. if Create Corridor is selected
By default, the corridor is built using simple assemblies consisting of just a road surface with no curbs. This is the case when Use Simple Road Assembly is selected. These assemblies are based upon the Civil 3D Primary Road Through Intersection assembly with right and left subassemblies renamed to offside and nearside in accordance with your driving convention.
Clear Use Simple Road Assembly to use more complex assemblies for the entry and exit roads. These assemblies are based upon the Civil 3D Primary Road Part Section – Daylight Right (or Left) again with right and left renamed to offside and nearside in accordance with your driving convention.
Normally you will probably want to construct the 3D model with calculated profiles; this is the default. To drape the corridor on the surface, select Drape Corridor on Surface. With this option enabled, the assemblies take their levels from the original surface profiles rather than the calculated profiles.
If Require Existing Surface is selected, the Corridor is only created if the Roundabout has is existing ground property set.
Select Use Curb Baselines to insert the assemblies on the nearside curb alignment. If cleared, which is the default setting, assemblies are inserted on the crown lines and targeted to the nearside curb and centerline alignments.
Require Existing Surface
Regardless of any of the settings, you can force a rebuild of all the selected elements by clicking Rebuild Now.