Surface modeling - Curbs with feature lines

[Srana123]

I am creating a parking lot and am having some trouble with the curb.  I created the graded parking lot which you see in picture 1. Now when I add my curb, the contours change to what you see in picture 2.

I created the curb line by turning the boundary around the parking lot into a feature line and picked up the elevations from this proposed lot. I then stepped offset that line by 0.1 and then raised it by 0.5 to show the front top of curb and then i offset that line by 0.5 to show the back of curb. I set these are breaklines and I got this new surface in picture 2.

How can I keep the contours from picture 1 while still showing the curb? Why do my contours change when I add the feature lines?

[Anonymous]

Did you add the curb feature lines to the proposed parking lot surface or start a new surface? I would think that if you added to the proposed parking lot surface it should work. Try turning on the triangle display (in surface style editor) to see what the triangles are connecting to.

[Srana123]

Thanks for the reply.

When I do the offset of the feature line, the surface seems to change without me adding the line as a breakline. Is this normal? 

Also I attached the before and after with the triangles showing. Something I noticed is that the triangles on the northern half of the lot look different from the southern but I think they should look the same since I graded each side to be 2% cross slope. Any opinions on this? I'm really confused about this.

Also another thing I noticed was after adding the feature lines, the triangles seem to move outside of the surface boundary.

[Anonymous]

Is there is any chance you used "relative elevation" when you draped the outer feature lines?

You might also need to check the "Supplementing Factors" you are using in the Add Breaklines Dialog box.  The defaults are pretty good sized and along the curve, with the horizontal distance so close to each other, the "interpolated" curves may be crossing.

Try dropping the Mid-Ordinate Distance down by a factor of ten.  We usually .1' unless we have some very large radius curves. (My understanding is that it generates a "tessellation" point at the radius of the curve x the Mid-Ordinate Supplementing factor)

As a side note, I never bother with three lines for curbs, just gutter line and back of curb.  Takes to long to make changes to three feature lines.  And because of the mid-ordinate problem.

Hope that helps

[maharoger]

i may have had a similar issue and it turned out to be the way the suface tinned (triangle hiccups). if you look at the contour lines with the triangles turned on you may find that where the contour line does the jog (from what it was pre-adding feature lines), the triangle edge needs to be swapped. also, have you looked at a quick section accross the curb feature lines to verify they are what you expect them to be?

[Anonymous]

It might be because of crossing feature lines. Look at it in 3Dorbit. Whenever feature lines that are in the same Site cross they have to account for each other, i.e. have the same elevation where they cross. It will drive you flipping crazy if you're not aware of it. Don't know if this is the case for you but get a 3d view so you can see what is going on.

[Srana123]

I checked my feature lines, there is one line running across the middle of my lot which I used to grade the lot with a 2% slope. I also have another feature line around the perimeter of the lot which took on the elevations of that graded surface so the point where the feature lines touch are at the same elevation. 

I also tried to mess around with the supplementing factors and mid ordinate distance but nothing really changes, I am still getting some weird contours.

[Anonymous]

I usually create a 3d wireframe model of things like parking lots, including curb & gutter or whatever other features will affect the surface. I spin it around in 3dorbit (save first) looking for errors.  I use grading objects and feature lines, as well as 3dpolylines. When I get it like i want it i will often use the grading objects (or corridors if that is the case) to extract feature lines or 3dpolys from then get it out of the picture. I know this probably isn't how it is intended to be used, especially if you have future edits, but I don't know a good way to add a grading object to a surface. But, once I get the 3d wireframe correct those feature lines and 3dpolylines are all I use for surface data (no contour data), as breaklines. It's pretty easy to see if it works by setting the contour interval to something ridiculously low, like 0.1'. Strange things are clearly visible then and I know where to concentrate my efforts to correct. this method may involve more work, like replacing the grading objects with breaklines, but my models are used for GPS machine control, so they HAVE to be right.

[Joe-Bouza]

FL grading and sites all work together and sometimes against each other. 

You have to be cautious of adding FL data to a grading; especially a projection.

your curb FL are in the same site and conflicting with the projection. 

There are several options and I cannot cover all of them. here is  a few that I use

1. use the surface plane of the projection to obtain the BC of the lot, curb offset (separate site), then add the curb and Crown FL to a FG surface. leaveing the projection surface as design updates accoringly.

2. use corridor with FL as baseline 

3. design the crown, then use the elevation tools on the ribbon the project 2"to the curbs ; then continue as in 1 or 2

[Anonymous]

My question to you would be why are you turning the boundary into a feature line? Why not just use the stepped offset command on the feature line you used to create the flow line? That is how I do it anyway...

[Anonymous]

If you didnt use feature line to create the outer flow line, then you can draw a poly line following your flow line, turn that into a feature line with elevations based on your design surface and then stepped offset that feature line for the top face and back of curb...