Introduction
In Civil 3D versions older than 2009, if a user chose the option
to create a feature line from one of the links of a corridor,
that feature line was cast into the design world with no trail
of bread crumbs back to the safety of its creator, the corridor.
That feature line was considered static and if the corridor
changed, those changes did not reflect through to the feature
line. In most cases, the prudent solution would be to erase the
feature line and recreate it with the new corridor geometry. To
make matters worse, if there were any design elements that
relied on the feature line, such as grading objects, then those
entities would have to be revised or recreated as well.
With the release of the 2009 version, users now have the ability
to create feature lines from corridors that stay linked to their
parent corridors. If the corridor were to change, then the
linked feature lines change as well. This is particularly useful
to the designers who create subdivision lot grading with feature
lines rather than with corridor subassemblies. The main idea is
to use a corridor feature line created from the back of curb or
sidewalk to launch the lot grading. The designer can allow the
free triangulation among the feature lines created for building
envelopes, ditches, swales, ridges, and slopes to create a
proposed surface covering the lots.
Application
Once a corridor has been created in a drawing, the user can
select the “Create Grading Feature Line from Corridor” tool from
the Corridor > Utilities pull down menu.
In the example above, the corridor was created with the
outermost links being the outside edge of sidewalk. This is
where our lot grading will begin.
Once the tool has been chosen, the user must select the link
(running parallel to the alignment) on which to create the
feature line. If two or more links are stacked on top of one
another in three-dimensional space, then the user will have the
opportunity to pick the correct link from a list. Once it has
been identified, the “Create Feature Line from Corridor” dialog
box will pop up with several choices.
The user can choose the site to attach the feature line to,
create a name for this particular feature line, apply a style to
the feature line, assign it to a layer, choose to smooth the
feature line, and check whether or not the feature link will
stay linked to the corridor. In this case, I have chosen to name
the feature line and keep it linked to the corridor; all other
options are default. Hitting the “OK” button here will create
the feature line and allow the user to select another link.
Hitting the return key here will end the command. This feature
line may now be used to create lot grading on the right side of
the corridor, and if any part of the corridor changes we can
rest assured that the feature line will update itself as will
the grading which depends on it.
Conclusion
Often times, our designs are more intricate than the uniform
grading offered by the “Daylight” subassemblies. The feature
line option gives the designer a bit more flexibility to shape
the terrain he or she is designing. As an applications engineer,
I am often asked about the best way to create roadside ditches
that meander or have profiles that are independent of the road
profiles. I can now reasonably suggest the option to shape that
ditch flowline with a feature line, then have the ditch banks
dictated by the simple triangulation between that flowline and
the feature line (and subsequent grading) created from the
corridor.
As designers and Civil 3D users, we are always looking for
different ways to accomplish our daily tasks. Sometimes we
settle back into our old ways if new techniques do not create a
boost in efficiency, sometimes the new methods get assimilated
into our bag of tricks. In this case, I think we will see more
of the latter.
