Sometimes if you build a corridor that has a complicated daylight or twisty baseline you wind up with “bowties” or little overlaps in the corridor feature line….

Sometimes you might run your assembly around your edge of pavement instead of down your centerline and have an overlapping centerline feature line…

A Road

You might want to extract a grading feature line or polyline because daylighting can sometimes be tricky around complicated corridors, or maybe you’d like to do some lot grading with grading objects and need that “base” feature line.

Or Sometimes you might want a a feature line but nothing else- such as in a parking lot corridor.

So how would you deal with this?  Press more to find out…

My Road Centerline…

I use Corridor>Utilities>Grading Feature Line from Corridor and choose my CL…

A grip edit on the extracted centerline reveals that since both sides of the road target that alignment, the feature line doubles back on itself.  Grading objects and even things like feature line stepped offset cannot handle twisty crazy feature lines that overlap and double back, or have duplicate vertices.  Trying to untwist such a feature line is an act of futility and I wouldn’t recommend it unless you have already finished all 6 Harry Potters and there is nothing on TV.  Bring a helmet.

My Parking Lot…

I might just be using this drive lane centerline as a guide and making a full blown assembly with lanes might be meaningless…

The solution:

 

Make yourself a Marked Point Only assembly. 

Add a baseline to your corridor that uses this assembly, making sure your feature line tab in the corridor properties box has a style assigned that will show up (it should by default).

Run your corridor again, and this time- extract the Marked Point feature line.  It should be untwisted and ready to extract.  You might have to view your corridor in isometric to see which feature line to grab, but by default they are often a different color from the other feature lines, so you should be able to identify it relatively easily.

For the parking lot you now have a feature line ready to extract or further improve your design. 

Make sure you build any surfaces to include feature lines (not just links) and choose the Marked Point.

If you’d like to see more about using Marked Points, I know there were a few Autodesk webcasts recently, and I have some posts that you might find interesting further reading.

Links and examples from my Feb 2 Webcast on Alternative Uses for Corridors (includes sample drawings and links to several river corridors done using marked points as well as traditional subassemblies)

http://www.civil4d.com/index.php/2007/02/links-and-downloads-from-feb-2-webcast/