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Lots of us in Civil 3D Land love to whine about Site Grading in Autodesk Civil 3D. Many of us still employ the classic design by breaklines methodologies from our CAD historical past to produce our production grading designs in Civil 3D. It works. These days most of us might agree that Civil 3D Feature Lines are an improvement over AutoCAD 3D polylines. Some folks may not agree.

Classic Civil 3D Feature Lines Grading Design

What are we talking about? Here’s a nice recent video example.


Generate Parking Lot Flowlines from a Grading

Nate Philbrick demos how to employ a Feature Line and a simple Grading to create elevations on Parking Lot Feature Line flowlines in Civil 3D. This is an inside out design approach.

Some of the design for the solution is managed a bit by employing an XREF drawing to hold the horizontal control.
If the parking lot layout changes, we can redo the flowline creation process.
The Civil 3D Grading that is employed to build the intermediate surface which generates those flowline elevations is simple enough and likely to remain stable.

Yeah. I’ve been known to poke fun at the Feature Lines Only crowd.

Site Design Corridors

A combination of Site Design Corridors and Feature Line grading design is nicer.

In Nate’s parking lot design solution, we might employ a simple Corridor with simple Assemblies that include Link or even Lanes subassemblies to build the resultant Feature Lines and Corridor Links to build the intermediate surface. Hope that makes sense.

I much prefer to manage the collected Feature Lines that we get from Multiple Baseline Corridors over trying to herd and manage the individual Feature Lines cats. Individual Feature Lines  are still confined in our Civil 3D projects to individual drawings.

DREF (data reference) Corridors allow us to employ their Feature Line dynamic or static results in multiple project drawings and explore more design options more easily. Yes. There is more Civil 3D management work involved to get there.

Another significant advantage of using a Corridor with Lane subassemblies is we get the top surface Feature Lines and Links and the subgrade Feature Lines and Links for multiple surfaces from the same better managed Civil 3D data behind. We do have more stuff to manage in the Corridor scenarios.

Another Site Design Corridor Approach

Horizontal and vertical control from a Feature Line in a Corridor Baseline is a wonderful thing.

Here’s another recent video with an outside in grading design approach. This employs Corridors built from design Feature Lines.


Civil 3D Dynamic Commercial Site Grading

The CADiot Savant demos how to employ Civil 3D Feature Lines and Multiple Baseline Corridors created from them to build a dynamic Site Grading solution in Civil 3D.

The video begins with some important AutoCAD polyline edit tricks and mechanics that Nate avoids in his useful demo.

This Corridors from Feature Lines solution results in more complex Corridors and/or Surfaces with Feature Lines produced from multiple Corridors, Usually we will end up with a combination of both scenarios.

In a real-world production project, we are probably going to want to manage our design control better than shown in this video. Just sayin’.

Better Site Grading Design

Our Site Grading Design Corridors post and videos series contains lots more helpful details, management tips and practices, and useful instruction for Civil 3D nuances like Frequency mechanics and Corridor Bow Tie fixes. The issues do arise.

Register and login for more Civil 3D help and documentation.

See the Civil 3D Corridor Site Design Considerations post, video, and get access to the entire Site Grading Design Corridors post and video series links.

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