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FeatureLine from Surface

FeatureLine from Surface

This is one of my wishes in the top of my list.


We can get a dynamic featureLine from a Corridor but we cannot get a dynamic featureLine from a Surface.



Imagine the following scenario:


I have a composite surface (with several pasted surfaces) that I name it "Surf1" .

I draw a featureLine on the surface and I get all the elevations of that surface for the vertex of the featureLine.


I add the featureLine as a breakline in another surface.


If I modify Surf1, I have to do every time "get elevations from surface" to update the elevations of the featureLine, so we need a dynamic featureLine from a surface.

Perhaps, it should be a new type of featureLine which is dynamic (automatic), it could be called: Surface FeatureLine.


In the settings for the creation of this featureLine and option about if he want remove all old elevations points and add a new elevation points every time that the surface changes.




I agree that it would be nice to have a direct way to do this.  But here's a method that I've used to accomplish what you're trying to do.


  1. Instead of creating the featureline and getting the elevation points from a surface, create an alignment.
  2. Generate a surface profile along that alignment.  This profile will remain dynamic to the surface so that when the surface changes the profile will also change.
  3. Create Featureline from Alignment.  You will be prompted for the horizontal alignment and the subsequent profile.  And this also includes an option to keep it dynamic to the profile.

Now you should have a feature line that will change elevations when the surface changes.  If you ever need to change the horizontal location, adjust the alignment as needed and the profile will change which will update the featureline.


P.S. Now add the featureline to the surface as a breakline and you're done.


Ohh yeah! 


I haven´t tried the third point.


However, I would like my idea without using an alignment.


More times, we have to make a lot of intermediate steps. 





@joantopo wrote:

However, I would like my idea without using an alignment.


More times, we have to make a lot of intermediate steps.  


I agree 100% it would really be nice to eliminate the extra steps of creating an alignment and a profile.


an option like this would have saved me a ton of time on a recent project.  The project actually had 4 different plan sets for submittal.  For contours to represent the way we desired the multiple surfaces had to be separated.  


scenario simplified:

3 different cad files with models.

file 1 was building and paving.

file 2 was earthwork grading outside of file 1.

file 3 was merged surface with data shortcuts to previous models.


Constant evolution of perimeter elevations of file 1.  File 2 was tied to perimeter of file 1 for grading.


The use of boundaries and other workarounds I was able to achieve what I needed. But a feature line generated from border of surface would have been nice.  I could break the feature line as necessary and make dynamic the segments.

On multiple occasions this very idea crossed my mind. 


I generally tell users to project feature line to surface with assign elevations and then explode and add to surface (delete and repeat if things change).  If it became dynamic, that's a game changer.


I typically use feature lines as draped boundary lines to match my design surfaces to EG surface. I also like to drape the featureline with intermediate points so that it is accurate.

It would be good to have...

a) the intermediate points added as level points (user-controlled). This way we can alter the shape of the feature line much more easily.

b) different colours on the glyphs for level points and PI points.This ould make it so much easier to find the PI points when making changes.

c) have a tick box somewhere to automatically get new levels from surface when the FL is moved

d) make it all much faster.  When there are a thousand or two points on the FL, even to select it it make changes takes a wait of minutes for long FLs.






Allow feature lines to have a datum depth parameter to more easily give accurate earthwork numbers for Site Grading.


It would probably be most efficient to have this editable parameter located in the Feature Line styles, with the abilty to override individual feature lines through Feature Line properties.


For example some basic Feature Line styles a User could have would be: Pave1 (6" datum depth), Pave2 (10" datum depth), Pave 3 (14" datum depth), Concrete1 (4" datum depth), Concrete2 (6" datum depth), Sod/Topsoil (4" datum depth).

Im not seeing how this one works @fcernst. How do the featurelines know to calculate a volume without creating a surface or creating a grading panel? Maybe the grading panels should have a depth parameter? so you can quickly calculate subsurfaces?


When the feature lines are selected to be added to a surface definition (typically to build FG), the subsequent Datum surface will be built and used in a Volume surface for earthwork calculations.


The Datum surface will react dynamically as the top surface feature lines are edited during grading design.


It's quite easy to build a surface and then move it down.

Or paste an FG surface into a Subgrade surface and then move it down.


Either way, the surface is dynamic to the featurelines and maintains its depth below them.


That doesn't work for land development site grading though, because the site top surface (FG) is composed of different materials with different material structural section depths (i.e., 6" asphalt over 9" base course, 4" concrete on subgrade, 18" riprap over 6" filter material, etc.)


OK, I get you.

In this office we've always used a separate surface for each zone with a different depth. But I could see the advantage of not having to split it all up.


How would you handle the step between different depths along the line between different materials? Could you have a line specifying both depths? Or just offset the line a minimal amount and have one line for each material depth? But then you'd have to deal with two lines to update when the grading is revised.


There would be Right and Left datum depths with respect to the feature line stationing, entered in the Feature Line style, with a convenient check box option to make the Left depth the same as the Right depth.


Cool, I like it.

Minor issue of how the TIN copes with a vertical step, but that'll be something the programmers can figure out.


Or perhaps setting a slope perameter for the step or a horizontal width should be part of the settings in the featureline properties? (Set to 10,000% for a virtually vertical calculation etc.)


Yes, we want the programmers to handle the vertical discontinuity for surface creation (much like Corridor overhang correction), so we don't have to inefficiently manage and worry about little offsets across a project, as is required with many of the Civil 3D "workarounds".


This feature line datum setup would quickly handle mid-stream requests to change surface materials and/or structural design depths for areas of the project.

Similar to:



Peter Funk
Sr Product Manager
Civil 3D
Autodesk, Inc.

Status changed to: Accepted
Status changed to: Gathering Support

More complicated aspect would be this:


Insert Intermediate Grade Break Points.


In theory, every time the linked surface is updated, then the "intermediate grade break points" would be removed and later add them again in the new intersections with the TIN triangles.


This way the FL is a true footprint every time the linked surface is modified.

Civil 3d must take into account the following points (exceptions).
- we cannot create a "surface feature line" from a linked surface if the FL is already being used as a breakline in the same surface.
- we cannot add this type of FL as a brekline if its linked surface is the same.

in both cases we will get a messagebox from Civil 3D about this to avoid circular loops.


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