Basics of Creating a Subassembly

The first thing you need to know about the Subassembly Composer is that the system is “drag and drop.”  As we develop our design we will need to pull the parts we need from the Tool Box into the Flowchart.  It is important to have a good understanding of subassemblies and code sets  before you begin working with the Subassembly Composer, so if you haven’t already read the first article in this series, please have a look at it.

Drag and Drop

The next part of the interface you will need to know is the Properties box.  Once you have placed something from the toolbox such as a point you can select the object in the Flowchart and the information about that object will populate in the Properties box similar to the way AutoCAD behaves.  From here we will be able to adjust how the object is created.

Properties box

Above, I’m working with a point, so I will be able to manipulate specific values.  The most important thing I can control is how the point is created.  Above, there is a section called Point Geometry Type.  The current method is “Delta X and Delta Y.”  This is just using an X and Y value in relation to another object.  Because this is the first object I’m creating, the only thing I’ll be able to locate this point by will be the origin or base point I’ll use when inserting my subassembly in Civil 3D.  The base point is called “From Point” under Point Geometry Properties.  The available value will adjust depending on the Type I select.  Keep in mind the delta values you specify here are in feet, not inches.

Once the point is located in the correct spot, we need to set codes for our first point. Under Point you can enter a value next to Point Codes.  For now, the value you enter here will need to be put in quotations.  This means that if you want to use the code Top, you will need to enter the value “Top”, including the quotations.

After you create your first point you will need to drag and drop more points to form the links and shapes of your subassembly.  Dragging a second point into the Flowchart, we can begin to look at some of the other location methods for our points.

Slope and Delta X

For my Second point, I’m using the Point Geometry Type “Slope and Delta X.”  This will allow me to follow a slope until I reach a horizontal offset.  If I used Delta Y this would be a vertical offset instead.

Under Point Geometry Properties, you can set the From Point value to adjust from what point this object is located.  As we continue adding more geometry, we will be able to select from all previously created points.

When switching the Point Geometry Type you should see the available Point Geometry Properties have changed based off of the Point Geometry Type.  In the image above, I have a Slope and Delta X value to set.

Again, we will want to set Point Codes if needed, but we should also look at the Link breakdown.  From here we can create a link automatically by checking the Add Link From Point check box.  If you do create a link make sure you add a value to Codes to specify what that link represents.

Now that we have begun creating links we should start paying attention to the Preview box.

Preview box

From here, you can select points and links to modify just like in the Flowchart, but this also gives you a much better feel for how the points all come together.

As you continue adding geometry you will eventually come to a point when you need to close your geometry with a link.  To do this we can just drag and drop a Link from the Tool Box.


When creating a link all we have to identify for its location is a Start and End Point under the Position breakdown.  Again, make sure you add Link Codes as needed.

Finally, if we are trying to make a shape to be used for volume calculations, we can drag and drop a Shape.


Once you add the shape, you will need to identify what links are used to make the shape.  To do this you can use the green selection option under Links and then select the space within the preview that you want to fill.  Think of it as creating a hatch.  Once again, we are going to want to make sure we set a code for our geometry.

Now that you have a functional shape with codes setup to work with Civil 3D, our next step is to give it a name.

You may have noticed in the bottom right corner of the screen that there are several tabs.  I am going to go into more details with these later in this series, but for now we need to switch to the Packet Settings tab.

Packet Settings

From here, we need to set the Subassembly Name.  Note this value cannot contain spaces.  Notice we can also give it a description, a help file, and an image for use in the tool palette.

Once we have given the subassembly a name, we can now save it out and import it into Civil 3D using the Import Subassemblies tool.

Import Subassemblies

From here, you will just need to navigate to the .pkt file and select what tool palette the subassembly will go in.

Adding to tool palette

From here, you should be able to use your very own subassemblies.


In the next article we will be implementing Parameters into our subassemblies to allow the user to adjust values directly in Civil 3D.

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