Assigning codes (e.g., "Top", "Flange", "ETW") allows Civil 3D to generate feature lines and breaklines along the corridor. 2. Links (L)
Drag a second below P1 . It defaults to P2 and automatically creates Link L1 . Change the Point Geometry Type to Slope and Delta X . Set From Point to P1 . Set Slope to GutterSlope . Set Delta X to GutterWidth . Add Codes: Point Code = "Gutter" ; Link Code = "Top" . Step 4: Create the Curb Face ( Drag a third Point below P2 . This creates P3 and Link L2 . Change Point Geometry Type to Delta X and Delta Y . Set From Point to P2 . Set Delta X to 0 (vertical line). Set Delta Y to CurbHeight . Add Codes: Point Code = "CurbTop" ; Link Code = "Top" . Step 5: Complete the Structural Loop ( Follow the same logic to close out the perimeter:
Create user-defined input and output parameters to control dimensions (e.g., width, slope) in Civil 3D. 2. Getting Started: The SAC Interface
Click on the corresponding links in your layout view ( L1, L2, L3, L4... ) to define the boundary. Set the Shape Code to "Curb_Concrete" . 5. Advanced Logic: Target Parameters and Decisions civil 3d subassembly composer tutorial pdf
Used to follow feature lines, alignments, or polylines horizontally.
The custom component is now ready to be added to any civil assembly string.
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[ Decision: Is P1 below Surface? ] / \ Yes No / \ [Construct Ditch Logic] [Daylight Slope to Surface] Create a named ExistingGround . Drag a Decision block into the flowchart.
Enter an expression in the properties field, such as: P2.DistanceToSurface(EG_Surface) > 0
Contains the building blocks (Points, Links, Shapes) and advanced logic (Decision, Switch, Variable). It defaults to P2 and automatically creates Link L1
Right-click on any blank space within the palette and select . Browse to your saved .pkt file, select it, and click OK .
The Subassembly Composer is a visual programming environment provided by Autodesk. It allows users to create custom subassemblies (the 2D cross-sectional geometry used in corridors) without needing to write code in C# or VB.NET. Instead, it uses a flowchart-style interface where you define:
What specific you are designing (e.g., a benching retaining wall, a complex highway median, or a custom sub-base layer).
AutoCAD Civil 3D is a powerhouse for infrastructure design, but its standard library of subassemblies often falls short when dealing with complex, real-world geometries. Whether you are modeling a unique retaining wall, a complex curb-and-gutter system, or a multi-layered highway section, the Subassembly Composer (SAC) is the essential tool for creating intelligent, parametric components. This guide serves as a foundational tutorial for users looking to move beyond "out-of-the-box" limitations and master custom subassembly creation. Understanding the Subassembly Composer Interface