Civil 3D – Sketched Cross Section to 3D Polyline

Civil 3D – Sketched Cross Section to 3D Polyline

Civil 3D – Sketched Cross Section to 3D Polyline

This came up on the Civil 3D discussion groups on the Autodesk Forums (HERE) not too long ago, someone asked if there was a way to take a sketched section in a cross section and make it a 3D polyline in the drawing to be used in a surface. The discussion went back and forth for a while until I got the idea to use the section editor for the corridor. Basically, you take the sketched polyline, make it a 3D polyline, copy it from the section view (or wherever it’s sketched), go into the corridor section editor, and paste it in there.

In the above image, the thick green lines are the hand sketched polylines that I want to use to make a surface. The key here is they are drawn to scale and there is a corridor that has a section at the location for the desired cross sections. Simply follow these five steps to accomplish this:

1. Convert the polylines to 3D polylines.
On the Modify Tab of the ribbon, expand out the Design panel and choose the command, “Convert 2D to 3D Polylines”. Select the polylines that were sketched in and they will be converted to 3D polylines for you.

2. Copy the new 3D polylines with a base point.

This is not the same as ctrl-V! We want to have control over where the copied objects are going once we paste them in. The command Copy with Base Point” is available on the Home tab of the ribbon but I typically use the right click menu to do it. Select one of the new 3D polylines (you’ll need to do these one at a time), right click, expand out the menu for “Clipboard” and then choose “Copy with Base Point”. When choosing the basepoint, choose something that you’ll be able to snap to, or at least identify, when you’re in the section editor. I recommend the insertion point of the assembly if that’s available.

3. Enter the section editor for the section the 3D polyline needs to go into.

Now that we have the data, we need to place it in the correct location. To do this, we’ll go through the corridor section editor. Select the corridor at the cross section you want to place the 3D polyline (grab the line perpendicular to the baseline alignment, not one of the lines that are adjacent to the alignment) and on the corridor ribbon, choose “Section Editor”.

4. Paste the 3D polyline in.

Once in the section editor, it’s simply a process of pasting the lines in. If you used the “Copy with Base Point” command, simply ctrl+v will paste the objects in and then place them where you need them to be. If you chose a basepoint with a common point in the section editor, you can snap to that.

5. Close the section editor.

Once the 3D polyline is pasted in, select the “Close” option on the Section Editor ribbon tab to return to your drawing. You should see the 3D polyline in your drawing now.

Hopefully this will help someone out and get everyone thinking outside the box when it comes to Civil 3D!


Brian J. Hailey, P.E.
CAD-1 Technical Specialist

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