Technical data

Chapter 5 Working with Surfaces
200
Key Concepts
■
No elevational information for the surface is available while an area
is hidden by a boundary.
■
Depending on how well the surface follows the boundary polygon,
you may want to make the surface boundary act as a non-
destructive breakline in order to trim the triangles exactly at the
edge of the boundary.
To contour around a pond by using a surface boundary
Steps
Use
to look up
1
Select the current surface.
Make a Surface Current
2
If the pond that you want to define as a boundary
is not outlined by a polyline, then use the PLINE
command to draw the boundary.
PLINE Command
3
From the Terrain menu, choose Edit
Surface
➤
Surface Boundaries.
Define Surface Boundaries
After Building a Surface
4
Type Add to add a boundary, press ENTER, and
then type
No
to not remove any existing
boundaries.
5
Select the polyline boundary.
6
You can specify that anything inside the polyline is
hidden (Hide) or shown (Show). For this example,
specify Hide, because you want to hide the area
inside the pond polyline.
7
You are prompted whether you want to create
breaklines along the edges.
By typing
Yes
, a non-destructive breakline is
created around the polygon boundary area. The
breakline trims the faces along the edge of the
boundary.