A boundary affects the visibility of the surface triangles inside it.
When you create boundaries, you specify whether they use arc tessellation and non-destructive breaklines.
Surface boundaries are defined from closed polygons, such as a closed polyline or a parcel, or from surfaces. Surfaces may be selected as boundaries when the Hide boundary type and the Non-destructive breakline options are both selected.
The surface definition displays the numerical ID and a list of vertices for each boundary.
Autodesk Civil 3D supports the following types of boundaries:
An outer boundary created using non-destructive breaklines:
A hide boundary created using non-destructive breaklines:
You can add more than one data clip boundary to a surface. When you add data, only the most recent data clip boundary is affected. A data clip boundary does not affect the visible part of the surface, but acts as a filter on all data, such as points and breaklines added to the surface after the creation of data clip. For example, if you add a breakline to a surface following the creation of a data clip boundary, only the part of the breakline that is inside the data clip boundary is added.