Surface Horror Stories (Civil 3D Trauma Bonding)

Kate Brown
Mar 9
2 min read

OK, I felt like writing examples of the surface carnage many of us have seen. Hopefully most Civil 3D users can at least get a chuckle — or cringe — from these.

Some of us have seen these first-hand, and when we were learning the software the problems were usually completely self-inflicted due to lack of knowledge and experience.

The “Entire County Surface” Project

Someone downloads LiDAR for the entire county. Didn't run the data through GIS or another processing software, just "let it buck".

Instead of clipping it, they build a surface from all 800 million points.

Then they paste that surface into the roadway design drawing.

Now every time someone zooms, Civil 3D tries to process the terrain covering 400 square miles.

The file is 2.3 GB. The mms file is 5.7 GB. And everyone on the project team bristles when asked to make even a text change in a file.

The Surface With 12 Million Breaklines

Breaklines are great for controlling terrain.

They are not great when someone converts every contour line into a breakline.

Now Civil 3D has to force triangulation across millions of intersecting breaklines.

Rebuild time: 4 minutes. At best.

For one surface.

The Surface Created with multiple DEM files and the vertical control was off per each DEM

Large tailings area that was flown by a client drone pilot. Pilot didn't set consistent vertical control.
Adding 4 DEM files into one file to paste together
Surprise! There is a 2-5ft vertical jumps between the data sets

Not technically a Civil 3D issue, but we see it and need to figure out a fix.

The Surface Snapshot Disaster

Someone hears that surface snapshots improve performance.

Technically true.

So they snapshot a surface built from 6 million points.

Now the drawing contains:

the surface definition
the cached triangulation (snapshot)
any edits added after the snapshot

File size doubles.

Rebuild speed improves slightly.

Everything else becomes slower.

The “Hide Boundary Will Fix It” Myth

A user realizes their surface is too big.

So they add a hide boundary around the project.

Problem solved, right?

Nope.

Civil 3D still processes the entire surface definition.

It just hides the triangles.

The software still remembers every single point.

The 10-Surface Stack

One surface isn’t enough.

So someone creates:

Existing Ground
Existing Ground Final
Existing Ground Final 2
Existing Ground Corrected
Existing Ground FINAL_USE_THIS_ONE

Then they paste them into each other repeatedly.

Now no one knows which surface is correct.

And rebuilding any of them takes F-O-R-E-V-E-R.

Final Thought

I hope this doesn't give folks nightmares, but we have all seen it and experienced it. We have hopefully learned from our younger, dumber selves and can move on and laugh at the past mistakes we have made.

Thanks for stopping by the Den.

Civil 3D: It’s not a bug. It’s a feature. Allegedly.