Graphics Programs Reference
In-Depth Information
understanding the 3D Chain
In Chapter 5, “Designing in 2D Using Alignments,” you used alignments to
design the 2D path of a linear feature, in this case a road. In Chapter 7, “Designing
Vertically Using Profiles,” you designed the vertical path of the road using profiles.
When combined, the alignment and profile form a three-dimensional pathway
called a
3D chain
. The 3D chain serves as the backbone of your design.
3D chains can actually be seen in your drawing, but only if you view the
drawing from a 3D perspective, as shown in Figure 9.1.
FiGuRE 9.1
The blue lines represent 3D
chains formed by combining alignments with profiles
to form a three-dimensional pathway.
Because the 3D chain is dynamically linked to both the alignment and profile,
a change to either one will automatically prompt a change to the 3D chain and
subsequently update the corridor.
understanding the Assembly
An
assembly
is a representation of the cross-sectional geometry of the feature
you're designing. It establishes the overall shape of the cross section and dis-
tinguishes the areas within it. For example, a typical road cross section can
have areas of asphalt pavement, base material, curbs, and sidewalks, as shown
in Figure 9.2.
FiGuRE 9.2
A Civil 3D assembly that establishes lanes, curbs, sidewalks,
and grading
