Autodesk continues it’s effort to implement BIM into their Infrastructure Design tools as they unveiled the market ready version of the Subassembly Composer for Civil 3D.

Autodesk Subassembly Composer for Civil 3D 2012 PresentationAutodesk’s Peter Funk, Dave Simeone, and Dana Probert hosted a preview for the Civil 3D Subassembly Composer yesterday. Most of us have heard about this tool, or seen it on Autodesk Labs, but not in all its release capacity. I was pleasantly surprised by this little tool, as there is a lot more capability packed in there than I had originally considered.

The Sub-assembly Composer is a stand-alone application that can develop cross sectional shapes which can be attached to a an Autodesk Civil 3D corridor. Why would you want to use this tool?

If you needed a new curb section, a better solution for daylighting, or my constant need: a retaining wall on one or both ends of your finished grade cross section. However, the application will develop any form of linear extruded shape that you have the time to develop. One example given was an I-beam.

Where, When, and How ?

The Autodesk Subassembly Composer for 2012 is a subscription only application, and is expected to go live on the Autodesk Subscription Center on July 7th, 2011. We may see it included in Civil 3D for the next release, but until then, you have to be a subscriber of Civil 3D, or an Infrastructure Design Suite that contains Civil 3D.

The Application will install with Civil 3D 2011 and 2012, but as you may have seen in comments made by  Mark Scacco and myself,  the product will not even install if Vault is present, This slowed us down a bit, only to find it pointed out in the presentation.

Composer Layout

The Composer layout interface is broken down into 5 functional sections:

Autodesk Subassembly Composer layout

  • Tool Box  –  contains all the tools associated with the composer.
  • Flowchart – the area where the Sub-assembly logic and structure are developed via drag and drop
  • Tool Properties –  Identification, Parameters, and Settings associated with the items in the Flowchart
  • Sub-assembly preview – A graphical cross-section preview of the shape being created, along with the related parametric feature identification to help visualize the component being composed.
  • Settings and Parameters – 5 tabs that drive the view to various information about Packet settings, Input/Output and Target parameters, Superelevations, and an event viewer.


The basic workflow of the composer is to drag a tool from the toolbox, such as a point, and adjust any parameters needed to compose the specification of the component.  Further tools are dragged into the Flowchart which add to the composition. points, Links, and Logic workflows are a few of the items that are available.

Autodesk Subassembly Composer Drag Tool image

When things get ordered improperly, links can be highlighted and pulled to new locations and even removed using the delete key. It really was designed in an easy to use format.

As tools are added, their properties can be modified as needed in the tool properties.

Autodesk Subassembly Composer Parameters

Here’s a few that I really enjoyed seeing:

  • Fillet Curve – Radius is an adjustable parameter, and as such can be modified as needed
  • Decisions – Logical analysis of queried information, and subsequent adjustments as defined
  • imageRoadway Mode Preview – Shows the layouts along with any target feature criteria that might be required by the sub-assembly. The existing grade surface plane will appear once it is introduced into the tools as a target. Then it can be dragged up and down in order to visually inspect how the logic and parameters react to the relative changes. So Nice !!!!!

Autodesk Subassembly Composer Roadway Preview

This image shows an example that was used during the demonstration. The EG surface was dragged up and down and the well established decision logic controlled and adapted the features flawlessly.

Warnings and Awareness

imageIn the event that something is dragged into place that is not ready, a red exclamation point  symbol is placed in the flowchart to show that something placed is not ready to be used, or is placed in an area that won’t work. Every example that I tried turned out to be very valid errors and not false alerts.

Another nice feature is a tooltip that appears over logic tools that shows the criteria applied. You don’t have to pick the tool, simply hover briefly and you get a quick understanding of what has been established.

image Autodesk Subassembly Composer Breadcrumb

Breadcrumbs are employed in the Flowchart area, which becomes really useful when digging through logic decisions. As you dive deeper into the logic complexity, the interface drives you into that layer, and removes portions of the upper level flowchart tree. The Breadcrumbs show you exactly where you are in the tree, and give you an easy way back to the top. I really appreciated this feature, especially when inside other people’s sub-assemblies.


Autodesk Subassembly Composer Help wikiAutodesk has adopted the Wiki as the main help backbone. Existing basic help and workflow profiles are already in place. Additionally, API function calls are included in the wiki, which I used a little to help me with a function query.

While my first impression of the Wiki help is not as great as the application. There was a lot of information there, but only in a general sense. Some examples were listed, but only in overview, and not the nuts and bolts. Most users would figure out the overview stuff themselves, but I hope that the wiki will be improved over time.

One good things is that in the API section, there appeared to be numerous already prepared examples to download and open, where API calls have already been established for you to use as a reference.  I used this one:

Distance to Surface calls in Sub-assembly Composer API Example

Autodesk Subassembly Composer ExampleI took their example and quickly adopted it into my decision for cut and fill states. Here’s a quick starter that I used.


In my real quick mockup I modified this I my decision like this:


This is then evaluated in a True of False state, that activates one link or another.

Importing into Civil 3D

imageCivil 3D will import these easily after the composer is installed, via a tool on the Insert Tab of the Civil 3D Ribbon. Composed subassembly files come with the extension of .PKT. For those that wish to use previously composed sub-assemblies, but did not wish to develop any themselves, there is a support pack available, that will allow Civil 3D to use the sub-assembly .PKT files. The reason for this is to install the API backbone with the additional logic calls associated with the composer.

One thing that needs to be mentioned is that any sub-assembly files that are downloaded from the help Wiki, and other locations that come with the extension .ZIP, may need to be renamed to .PKT.

Additional Capabilities

Beyond the obvious ability to develop any shape and logic you desire in your corridor models, additional API calls are built into the Subassembly Composer such as angular references related to referenced surfaces, that will give your Civil 3D corridors a lot more power and flexibility that you had with the installed versions of Civil 3D 2011 and 2012.

Comments, Links, and Screenshots

This tool is really cool, and gives Civil 3D users an easy method to develop sub-assemblies with more control and capability then was ever available before. Flexibility is off the chart. Not only is it great for custom, one-off sub-assemblies, but even developing standard models is easier in this interface than in Civil 3D.

What will Autodesk do with this BIM tool in the future? They are not saying, but the implications would appear that other BIM oriented applications would be able to utilize these shapes in the near future. My first thought is Revit Structure and the Civil 3D Bridge Modeler.  We’ll see.

Here are a couple more screenshots from the presentation.

Autodesk Subassembly Composer Screen Shot 1 Autodesk Subassembly Composer Screen Shot 2

Link to the Autodesk Subscription Center

Link to the Sub-assembly Composer Wiki Help

Link to Dana Probert’s Fun spin through the Sub-assembly Composer