Which of the following is a boundary type for Civil 3D surfaces?

• A. Proximity
• B. Outer
• C. Breakline
• D. Inner

Answer: (D)

In Civil 3D surfaces, a boundary controls how the surface is limited and how its triangulation is generated. An inner boundary creates a hole within the surface area, meaning any triangulation inside that boundary is suppressed and the surface has a void there. This makes inner a valid boundary type for shaping the final surface.

It’s also helpful to know other boundary types: an outer boundary defines the outer limits of the surface, and a breakline boundary uses a linear feature to influence how the surface is triangulated along that line. Proximity, on the other hand, isn’t used as a boundary type.