Creating a Simple SAC | Autodesk Civil 3D Subassembly Composer

In this blog post, we will review how to create a subassembly using basic geometry (advanced geometry will be covered later).

If you need a walk-through of the Subassembly Composer user interface, click here. If you need a walk-through of Subassembly Composer packet settings, click here.

To watch a video tutorial on how to create a SAC, click here.

In this example, we are creating a subassembly for a sidewalk. Below are the parameters:

Now, we're ready to add the geometry!

1. Open Subassembly Composer.
2. On the left of the screen, you'll see the "Tool Box" window. In that window, we'll work with the "Geometry" tab. Begin by selecting and holding "Point" and dragging and dropping it under "Start" in the flowchart. This will be our starting point.
   
   
3. Now you have a starting/origin point. You'll notice in the "Properties" window, some of the point information is populated. Under "Point Codes", define the code. In our example, we entered '"Top"'.
   
   
4. Since this first point is our starting point, leave the "Point Geometry Properties" as "Origin". 
5. Drag another "Point" under the origin point. This will create a second point titled "P2&L1", which means "Point 2 and Link 1".
6. Here we have to essentially tell the point what and where it is. In the "Properties" window, under "Point Geometry Type", select "Delta X and Delta Y".
   
   
7. Now we will set the changes in "Delta X" and "Delta Y". This is where the previously set "Input/Output Parameters" come into play. For our sidewalk example, we're going to define the planter geometry properties. In the "Input/Output Parameters" window, select and copy the "PlanterWidth" parameter and paste it in "Delta X" under the "Properties" window. This now gives us the ability to change that property in Civil 3D.
   
   
1. In this specific case, since we're doing a swale in the center of our sidewalk planter, we want to only do half of what we've set for "Delta X". To do this, enter a formula into "Delta X" by adding "/2" next to the already copied "PlanterWidth". The end result should read "PlanterWidth/2". You'll notice the change in the "Preview" window. Now, regardless of what the "PlanterWidth" is, this point will always sit at its halfway point.
   
   
8. In "Delta Y", copy over the "PlanterDepth" parameter from the "Input/Output Parameters" window.
9. You'll notice in this example, the planter depth increased. For cases where we want that to go down instead of up, enter "-" next to the already copied "PlanterDepth" in "Delta Y".
   
   
10. Add a point code for this point. In our example, we entered a double code: '"Top" "FL"'.
    
    
11. Add another code under the "Link" tab. In our example, we entered '"Planter"'.
12. Add a third point. Enter a point code. In our example, we entered '"Top"'.
13. Repeat steps 7 and 7.1.
14. Repeat step 8 as well, leaving "Delta Y" positive. This creates the swale.
    
    
15. Now we can build the sidewalk. Add a fourth point and place it under your third point.
16. Enter a point code. In our example, we entered '"Top" "SW"'.
17. Copy "Sidewalk Width" into "Delta X" and "Sidewalk Slope" into "Delta Y".
    
    
18. Under the "Link" tab, enter a code. For our example, we entered '"Concrete"'.
    
    
19. Add a fifth point. This will define our sidewalk depth. Change the "From Point" to "P3".
20. Copy "SidewalkDepth" to "Delta Y" and make it negative by entering "-" next to the already copied "SidewalkDepth". There will be no change for "Delta X" for this point, since it's just for the sidewalk depth.
    
    
21. Add a point code. For our example, we entered '"Datum"'.
22. Add a sixth point. Change the "From Point" to "P4".
23. Repeat step 20.
    
    
24. Enter a point code. For our example, we entered '"Datum"', just like for P5 (point 5).
25. Now drag a "Link" from the "Tool Box" and drop it under P6.
26. Select "P5" as the "Start Point" and "P6" as the "End Point". This will link P5 and P6 and close the object. We'll add a shape to that closed object later on for quantity take-off purposes.
    
    
    
27. Add a seventh point. This will be our subbase. Change the "From Point" to "P5".
28. Copy "SubbaseDepth" to "Delta Y" and make it negative by adding "-" at the beginning of the already copied "SubbaseDepth".
29. Enter a point code. For our example, we entered '"Subbase"'.
30. You'll see that it's not linked. To link it, check the "Add Link to From Point" box under the "Link" tab.
    
    
31. Add an eighth point. *No worries! We're almost done!* Change the "From Point" to "P6".
32. Repeat step 28.
    
    
33. Add a link. Select "P7" as the "Start Point" and "P8" as the "End Point".
    
    
34. Enter a point code. For our example, we entered '"BotSub"'.
35. Add a ninth point and change the "From Point" to "P4".
36. Enter a point code. For our example, we entered '"Top"'.
37. Copy "BOWWidth" to "Delta X".
38. Check the "Add Link to From Point" box under the "Link" tab.
    
    
39. From here, you can add a slope, if you'd like. To do this, add a new parameter in the "Input/Output Parameters" window and name it "BlvdSlope".
40. Change the "Type" to "Grade" and set the "Default Value" as "5.00%".
    
    
41. Now, back to P9, copy "BlvdSlope" to "Delta Y".
    
    

But now we need to add shapes. We need to this for quantity take-off purposes.

1. From the "Tool Box", click and drag "Shape" to the flowchart under "P9".
2. In the "Properties" window, enter a shape code. For our example, we entered '"Concrete"'.
3. From here, you can add all of the links individually or click on the green icon next to the links text box. This will allow you to select the shape you want.
   
   
4. Select the top shape in the subassembly. This closed object will now be known as "Concrete".
   
5. Add a new shape and enter a shape code. For our example, we entered '"Subbase"'.
6. Select the green icon next to the links text box and select the bottom closed object. This is now our subbase.
   

Now we can see the full assembly you've created. It's also possible to build this in Civil 3D, but it would have taken several subassemblies. We now have one complete subassembly that is dynamic and easier to use in Civil 3D.

To learn more about Subassembly Composer and explore additional tools, click here.