Breaking through the Roadblocks

AutoCAD® Civil 3D presents numerous roadblocks to a successful implementation of BIM, but with customization one can break through these obstacles.

Once upon a time I started a blog on Civil 3D called Civil 3D Reminders. After a few years it became evident to me that the blog wasn’t so much about Civil 3D as it was about modifying Civil 3D to get it to do what it couldn’t do intuitively, or at all. I wrote numerous examples about how to create complex label styles to derive information from the model using expressions. Other posts covered how to utilize the Application Programming Interface (API) to fill in the holes in the product’s capability for creating civil engineering designs.

Ideas for posts came from solving problems for my own struggles in meeting the plan requirements in the Southern California area. Other ideas came from spending way too much time in the Autodesk Civil 3D Discussion Group.


BIM was rarely mentioned in the beginning, mainly because Autodesk Marketing avoided the BIM label on Civil 3D. Civil 3D, in my opinion, isn’t a BIM product. At its core, Civil 3D is a labeling engine. Civil 3D is a tool to make labeling the required information on the plans. The design process utilizes a limited feature set of real-world objects used in construction. It is extremely limited in its ability to be a true BIM product.

There are curbs, but no driveways, there is linear sidewalk for roadways, but you are out of luck for nonlinear work such as apartment complexes. Many of the real-world objects are approximated through surfaces. Surfaces are greatly restricted on their ability to convey designs. Surfaces can’t have vertical surfaces or points occupying the same XY location with different Z elevations.

I find it hard to believe with the amount of marketing Autodesk is putting into marketing Civil 3D as a BIM product that new features aren’t rolling out in the yearly release cycle. There have been UI improvements in the product, but outside of pressure pipe networks there hasn’t been a flood of BIM objects.

The development of a conceptual civil design tool, Autodesk Infrastructure Modeler, has done little to improve the feature set for doing BIM designs. Sure, I can easily create a roadway, but the tool provides little improvement to the capabilities of a corridor in Civil 3D. It saves me a few steps, but what I needed was to have the ability to easily add a retaining wall to my corridor or allow flexibility in changing widths that stick and are intuitive to review. Anyone who has applied overrides to a corridor is sure to regret it when revisions have to be done. For those overrides need to be done over and over again to reflect the new design. 


So what is one to do? One way to overcome these problems is to create your own tools or have someone else do it to fill in the gaps. One example of a tool developed for curbs is by Quux Software. I have not worked with this tool, but I have contributed to other commands within Quux Software’s offerings. The CreateCurbs command helps automatically create the appropriate feature line offsets for curbs and creates surfaces from them. After being offset, the feature lines are then added to the surface. This automates some of the pain of having to create parking lot surfaces by automating part of the process. This tool doesn’t create a BIM object, but creates feature lines that Civil 3D uses to model a surface.

Pipe Networks

Pipe networks, one the first features in Civil 3D, unfortunately has received little to no attention when it comes to added features. Part Builder is supposed to allow users to create their own parts to use in Civil 3D. I’ve heard mixed reviews about the ability to modify existing parts or part creation with this tool. One company to provide a set of parts is CAD-1, which has created a Part Library for use in Part Networks for a variety of objects.

Another pipe network feature that I find difficult to use is Pipe and Structure Rules. Navisworks heralds the ability to do clash detection between objects. With Autodesk having a product whose main feature is clash detection one would think Autodesk would put development into pipe rules to avoid clashes. Unfortunately, pipe rules are oblivious to objects outside their connections. It is almost like Autodesk wants civil engineers to contaminate the water by not providing tools to make sure the water line stays a minimum distance apart from sewer lines as required by health regulations.

It’s long been on my list of customization tasks to change this. Hopefully someday I will find some time to do it. In the meantime this is one area of customization that is available to be done within Civil 3D. All of the pipe and structure rules are customizable. Once can create rules that do look out for obstacles and not only warn you about them, but also adjust to avoid them. That is not to say that I haven’t done my share of pipe and structure customization. I once worked on two to three hundred lot subdivisions. The local sewer agency requires inverts be shown at the property lines. When changes happened to a main, the changes to those invert elevations became a time killer. So I could get back to working on things I enjoy more, I created a pipe rule to adjust the sewer lateral to the main line pipe.

This worked great at first, but it became troublesome to go through and apply the pipe rules to all of the pipes. There had to be an even better way to go. I rolled up my sleeves and went to work to create a dynamic solution to the problem. Today, after I’ve created a sewer lateral pipe network, my sewer laterals adjust to any changes in the main line sewer line.  This saves me countless hours of manually adjusting labels and makes the product a little bit like a BIM product.


Surfaces are screaming out for customization. After working in construction for an earthwork contactor it baffles me how hard it is to get accurate quantities for non-roadway projects from a supposed BIM product. Sure, the process to calculate the quantity of earthwork between two surfaces is extremely easy. But as the saying goes: “garbage in, garbage out.” On the plans we show finish grade contours, but need to calculate earthwork quantities on a datum surface or subgrade surface. This requires a lot of extra manual work, and if the work isn’t done, earthwork quantities will be off by a large amount. A balanced site using the finish grade and existing grade surface can become an unexpected import or export project, which could have been avoided. 

The process of creating these datum surfaces can be streamlined through customization of the product via the API. One way to do this is to create polylines around the areas of different types of materials and thicknesses. Then copy the finish grade surface for each one of those areas. Then use the polylines to create boundaries around the areas, drop the surfaces the corresponding amounts, and then paste all of the surfaces together. While still not an ideal solution, it saves some time in generating earthwork quantities. A sample of the customization may be found in my free, discontinued, Civil 3D Reminders Pack on my website.


Civil 3D isn’t quite ready for prime time when it comes to being a BIM product. With some customization we can help the product along to start to fulfill the promise. Using the API it is possible to have Civil 3D design objects or perform the design steps for you. This improves your productivity and frees you to design rather than manage objects.

Appears in these Categories