Drape 2D Polyline

[Anonymous]

I would get a lot of use out of a command that would "drape" (e.g. raise/lower) a 2D polyline that crosses a selection set of other polylines which have differing Z elevations, thus turning it into a 3D polyline (think of drawing a 2D polyline down the centerline of a ditch on a contour map, and then running this command on the polyline which would turn it into a 3D polyline and change its vertices to the correct elevations so that it "lays" on the contours where it crosses, and any intermediate points are interpolated between the crossing points).  This newly created 3D polyline could then be used to add to a surface as a breakline that helps correctly model the terrain.  And there are MANY other uses for these.

I've asked if this command exists back on November 10, 2011 when I was new to Civil 3D (you can see the original question and responses here).  In fact, Terry Dotson of Dot Soft, in reply #11, said back then that they just had added this type of command to their software.  So this idea must be useful.

I realize that a few Civil 3D commands exist, like "Set Grade/Slope Between Points" and "Create Feature Line from Object" which do some of what I need, but they each have specific limitations and just do not fit the bill. 

[Anonymous]

Have you tried turning the selection set of polylines into a surface, and then create a feature line using your polyline you want to drape, and have it asign elevations? That might work...

[troma]

Convert all the 2d polylines (contours) to featurelines.  They should inherit the elevation of the polyline.  Make sure  they are all on the same featureline style.

Then convert the 'breakline' to a featureline in the same site, but on a different featureline style.

Then go to the site in your prospector.  Expand the site, and right-click on "Feature Lines".  Choose 'Properties' and go to the 'Options' tab.

In here you set the priority of the feature line styles for that site.  Move the style for the contours to the top, and the breakline to the bottom.  This will ensure that the contour featurelines dictate the elevation for the breakline, and not vice-versa.

[Anonymous]

Norwestcorp-Den:  Yes, making a surface then adjusting the feature line to the surface will technically create a 3D polyline, but it has some flaws.  By making a surface of only the polylines (contours) first, the resultant ditch within the DTM model does not have any breakline to define its low points.  That is why I want to drape the 2D polyline onto the contours first before making the surface.  If I had a command to turn a 2D polyline into a 3D polyline at the correct elevations (before creating the surface), I could use the contours to start the surface, then add the 3D polyline as a breakline, thus adding more accuracy to the DTM because the triangulation would be forced to recognize the breakline. 

I know that I can make the surface from the contours, and then adjust a feature line onto the contours, but because the surface is first created without the 3D polyline running down the center of the ditch (in my discussion example above), the surface does not correctly model the low points between contours, especially if the ditch is curved (not in a straight line, or has a long distance between contours at its centerline.  In both of these scenarios, the triangulation will occur across the width of the ditch because of the close proximity of the adjacent contour vertices.  That is where the 3D polyline comes in handy.  If used as a breakline, it forces triangulation to the lowpoint of the ditch line, and thus the digital terrain model correctly mimics the flow line.  Yes, I can o-snap a 3D polyline from contour to contour, and that works great if the ditch is in a straight line, but most existing conditions are not in a straight line.  They bend.  And picking 3D polyline vertices between where they cross contours causes them to have a 0 elevation for the Z coordinate.  There is a command named "Set Grade/Slope Between Points", that would correctly change the 0 elevation of intermediate vertices but using it requires a lot of manual labor because you would have to apply the command to the centerline independently between each and every contour. 

As is detailed in my forum topic from 2011, I work for a construction company that bids earthwork projects, and have to deal with a lot of existing grade contour maps provided by design engineering firms. And they typically do not provide points and breaklines, just contours that were interpolated from that data, that were in turn, provided by a third party surveyor.  There are too many "fingers in the pie" to request point files and breaklines, and not enough time to get them as we are usually in a competitive bidding environment.  Thus, I have to work with what I am given.  Therefore any tools or commands that help me in this process is greatly appreciated. 

In my case, it all comes down to being able to easily create a 3D polyline that includes intermediate vertices which correctly model the ditch centerline before the surface is created.  That way, I can include it as a breakline within the surface definition. 

Troma:  the issue is creating the breakline with the proper Z elevations at all of the vertices.  If the breakline is created by adjusting it to a surface that contains an incorrectly modeled ditch (because there were no breaklines to begin with), then it just inherits the incorrect Z elevations.  The incorrect Z elevations that I am referring to is the triangulation across the width of the ditch because there was no breakline to force the triangulation to the V shaped bottom portion of the ditch.  

Sorry for the long post, but thank you for your interest and replies.

[troma]

I understand the incorrect elevation due to missing breakline data.

Read my previous post again. My method does not involve the creation of a surface and draping to the surface.

[Anonymous]

Thanks Troma.  I will read your post again, and try the process. 

[Anonymous]

Troma,

I tried method you described using feature line styles.  The result was that the breakline inherited the contour feature line's elevations, but only at the vertices where they crossed. See split viewport image below (plan view over 3D view).  The intermediate vertices, which were drawn to follow the meandering flowline) all stayed at the zero elevation at which they were drawn.  What I hoped would happen is that the intermediate vertices would have been assigned elevations that were along the slope between two adjacent contours at the flow line of the ditch.

This meandering, curved shape of ditches/streams etc. require intermediate polyline vertices to approximate the meandering flowline around bends.  The command I seek would adjust the vertices to the elevations of the contours where it crosses, and any intermediate points to the appropriate elevation along the calculated slope (G=D/L, or  "slope = drop/length").

[troma]

I was wondering how much meander you had. I hoped that mostly you would hit the next contour before you had to bend, but looks like that's not the case.
Do you know of the button to flatten the grade? This will work for sure to interpolate the correct elevation to all those intermediate vertices. But maybe it's more work than you want; you were looking for an automated tool I understand.
http://docs.autodesk.com/CIV3D/2013/ENU/filesCTU/GUID-6C1968B7-168D-4608-BBE1-1C03413E0CA0.htm