AutoCAD Civil 3D: Stop and Smell the Tricks

Often we get so engrossed in outputting work we forget to stop and smell the tricks. The tricks are functions we use in AutoCAD® Civil 3D® that may not be obvious at first, but that ultimately make our lives easier. Tricks might be using expressions to get rid of the manual movement of labels or finding a quick and easy way to trim blocks.

What that, let’s get to it.

AEC Tricks

One of the earliest tricks I learned about was the AEC Modify Tools located on the right-click menu in Civil 3D. Using the commands, we can get enhanced capabilities in using Trim, Extend, Divide, and other commands. I find the Trim command especially helpful in trimming blocks and linework. The command lets you select what you want to trim and then select either points on the screen or pick a line on the screen. Then you select which side to trim. This works extremely well on blocks. It trims all of the items contained with the block and makes it an anonymous block.

The Extend command is great for extending linework without having a line to extend to in the drawing. It works by selecting a boundary edge on the screen. I found this especially helpful when needing to extend to a profile. Normally Civil 3D has trouble extending to some Civil 3D objects, but with this command we can extend to some of those objects without creating temporary linework.

Now that you know that trick is there, take the time to smell the tricks and learn others that can help in your day-to-day work.

Undocumented Tricks

Have you ever wanted a flexible mask object, one where you can grip edit the edges to new places? Well there is such a command within Civil 3D that does just that. Unfortunately, it’s undocumented in Civil 3D, but it is documented in AutoCAD® Architecture. Since it is not in the help file I’ll go through one way to create it. The first step is to draw a polyline around the area you want masked. Then type AECPOLYLGON at the command line. Type C for Convert, then PL for Plines, and then select the polyline that you created. Once created, the style of the AECPOLYGON needs to be created for the mask. To do this, type S for Style to bring up the Style Manager (see Figure 2). 

Figure 2: Style Manager

Then select the Standard Style and choose Use Background Mask under the Other tab. Pressing OK will make the Standard AEC Polygon Style be a mask. Now we have a mask object, but we probably want the edges to be hidden. To do that, select the AECPOLYGON and then right-click and choose Hide Edge from the menu. Then go around and select the edges to hide. The edges will go from green to red once hidden. This makes it easy to hide building pad areas from a surface.

A colorful, undocumented tool is the LineWorkShrinkWrap command. This command makes it easy to create a polyline of a batch of linework. And it’s a snap to create a line encompassing numerous extracted surface boundaries. For instance, I was working on a levee project. Since Civil 3D isn’t really a BIM product with actual real-world objects, I had to come back later and add ramps from the bottom of the levee to the top to a corridor surface. This left me with about 32 ramp surfaces and a corridor surface object. In order to make sure I didn’t have any errant triangulation in my overall surface I needed a boundary that encompassed all 33 surfaces. To do this I extracted the surface boundaries, converted them to 2D polylines with the same elevation, and then used the LineWorkShrinkWrap command to create an outer polyline of the surfaces. I then used this polyline as the outer boundary of my composite surface. It’s important to use 2D objects since the command doesn’t like 3D lines.

The Obscure

About once a year Autodesk® releases Subscription Advantage Packs. The packs extend the functionality of Civil 3D with new features before the next release. Often they are features that would normally be introduced in the next release, but come out a bit early. This year’s version was the Volumes Dashboard Extension for AutoCAD Civil 3D 2012.

Unfortunately, it doesn’t magically appear within Civil 3D when it is released. You must go to the Subscription website, download it and then install it. While you are there getting the download, make sure you check out the other extensions available. If you work with other data formats such as GENIO and 12d you will also find tools for your use. If you’re stuck using an older version, check to see if there is a Subscription Advantage Pack for your product.

The Subassembly Composer was released as a tool for use in furthering the abilities of subassembly. The tool makes it easy to create subassemblies that do exactly what you want (or close to it) without a lot of programming. I’ve used it to create subassemblies that contained all of CALTRAN’s curb types. That way I won’t have to swap out a subassembly if the design changes. All I have to do is select the curb type I want to use from a drop-down list. I also know that the dimensions are correct. Other custom subassemblies I’ve created are for retaining walls that look up standard values of standard plans, so I don’t have to continuously look up the values.

Autodesk Labs also has some limited-release products to help make our lives easier. For instance the Corridor Solids Technology provides a way to get quasi objects from a corridor. While the solids are not exactly smart objects, they are objects that better model asphalt pavement. When was the last time you saw asphalt pavement made of lines and points?


Expressions are my “go to” trick. If I don’t see a way to label a Civil 3D object within the program, expressions are the first things I consider.  My list of expressions is quite vast. I’ve created vertical curve labels that label every 50 feet along the curve. That way I don’t have to place numerous labels that an agency may require. I’ve created pipe labels that are anchored to the invert of the pipe at the outside edge of a structure, reducing the amount of time required to label a pipe network.

Expressions may also help do calculations. Using expressions we can create an expression to calculate the flow of a pipe. Sure it’s a long equation, but it is possible. Another expression for calculations is for calculating stopping sight distance for use in vertical curve labels. This way we can check in the label if the stopping sight distance is exceeded.

There are some great resources out there on how to create and use expressions.

Hopefully you can take the time to investigate how tricks might help make you more productive. Also take the time to look for other tricks that are out there. Here’s one place to start: Peter Funk usually has an Autodesk University class on tips of tricks within Civil 3D.

Christopher Fugitt is a Civil Engineer and has spent the last eight years designing government projects as well as residential subdivisions. Before working as a Civil Engineer, Christopher worked for a General Engineering Contractor on subdivision and mining projects. Christopher earned his B.S. degree in Civil Engineering from California Polytechnic State University, San Luis Obispo. Christopher maintains and authors the Civil 3D Reminders blog at

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