Author: Gaurav Bagga AutoCAD Civil 3D, AutoCAD

While working on a grading I needed to change grades along a path that had been defined as a 2D polyline. Well, it is a fact that a 2D polyline cannot hold different elevations at different vertices. This is a property of a 3D polyline. So, is there a way convert the 2D polyline to a 3D polyline? Yes, there is!

I was reminded of two fantastic and very old tools that would let you do just that – Convert 2D polyline to 3D polylines and Convert 3D polyline to 2D polylines.

They are both found under Ribbon tab “Modify” > Expand “Design” Panel Title



After you convert the 2D polyline to a 3D polyline you can then assign different elevations to the vertices per your design.

And if you need to work with grades instead of vertex elevations, you can also convert the 2D polyline to a Civil 3D Feature line using the command Create Feature Line from Objects found under Ribbon tab Home > Design panel > Feature Line flyout.



However, there is one important thing to note when you convert a 3D polyline to a 2D polyline. The new 2D polyline takes the elevation of the start point. Which means you would lose individual vertex elevations of a 3D polyline. This is very similar to the flatten command, except the elevation of the first vertex is maintained instead of pushing everything down to “0” elevation.

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     Gaurav Bagga
Gaurav Bagga
Senior Application Specialist Infrastructure

Gaurav is a Senior Application Specialist for Infrastructure Solutions at Ideate based out of San Francisco. He has over 18 years of experience in construction and related software industry. With this extensive design technology background he helps engineering and surveying companies, federal and state government agencies, and ENR 500 firms critically analyze and improve their construction drawing production process. He implements Civil infrastructure design technology led by InfraWorks and Civil 3D and has helped Ideate grow Civil Infrastructure Services. Being an industry recognized speaker he has presented cutting edge design technology at several industry conferences such as Autodesk University. Find Gaurav on Twitter.