AutoCAD Civil 3D General Discussion

AutoCAD Civil 3D General Discussion

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doni49
Posts: 1,955
Registered: ‎12-22-2012
Message 1 of 18 (249 Views)
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Two breaklines at same elevation. Large Gap between. Contour zig-zag btwn.

249 Views, 17 Replies
05-21-2014 12:20 PM

I'm finally at the end of the grading work for this lake regrading project.  But I've got one issue left that I'm stumped on.

 

In the following image, you'll see three breaklines set @ 822.  There is a rather large gap between them (this is supposed to be FLAT.  But the 822 contour is doing a zig-zag back and forth between the breaklines.  Since the breaklines are AT 822, why won't the 822 contour just follow the breaklines around?  The second image is the same area showing the triangles.  I snapped at the ends of all the triangles in the area and both ends of each triangle are at 822.

 

ContourZigZag.png

 

ContourZigZag_Triangles.png

Don Ireland



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You have crossing breaklines all over the place, coupled with contradictory data at the Jetty boundary..

 

 

 

 

Capture.JPG

 

 

Capture2.JPGCapture3.JPG

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Neilw
Posts: 2,322
Registered: ‎09-04-2006
Message 2 of 18 (234 Views)

Re: Two breaklines at same elevation. Large Gap between. Contour zig-zag btwn.

05-21-2014 01:56 PM in reply to: doni49

Those little anomalies are common with TINs. Try adding a few points or breaklines that are slightly higher or lower than the contour to that area.

Neil Wilson (a.k.a. neilw)
Infrastructure Suite/C3D 2013, LDT 2004, Power Civil v8i SS1
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HP Pavillion h8xt, i7 2600, 12 GB
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doni49
Posts: 1,955
Registered: ‎12-22-2012
Message 3 of 18 (228 Views)

Re: Two breaklines at same elevation. Large Gap between. Contour zig-zag btwn.

05-21-2014 02:13 PM in reply to: doni49

I've continued to troubleshoot this and have found something that I think is at least PARTIALLY responsible for this.

 

This is a man-made lake that's being regraded.  In the first image, you'll see a "top of bank" closed polyline that goes around the lake.  Then you'll see a Bottom of Shoreline Slope (Green) that also goes around the lake.  The Bottom of Slope is at 822. 

 

LakeOverall.png

 

Then there's another closed polyline (black) that goes around the lake INSDE of the shoreline.  This is also at 822.  The surface is FLAT between these two.

 

That all works fine until I add my jettys.

 

One jetty will result in the 822 needing to split off on both sides of it.

 

The bottom of each jetty is at 822 until it hits that black breakline.  Once inside that breakline, the bottom of the jetty follows the EG surface.

 

The second image shows what I'm talking about there.  The red lines represent kind of what the 822 contour needs to do.  The blue line represents what the 821 contour looks like (to keep the breaklines clear, I've turned off the triangles and contours).  These images are of plot previews.

 

Jetty1.png

 

EDIT:  I've uploaded my files to dropbox.  This link will have a zip file containing two dwg files.  The one I'm working in is the DESIGN file the SURVEY file contains the EG surface which is d-ref'd into DESIGN.

 

https://www.dropbox.com/s/i5jzasy4wmm0la5/LakeGrading.zip

Don Ireland



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My File is too large to post or I can't post it due to privacy issues!
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Neilw
Posts: 2,322
Registered: ‎09-04-2006
Message 4 of 18 (205 Views)

Re: Two breaklines at same elevation. Large Gap between. Contour zig-zag btwn.

05-21-2014 03:50 PM in reply to: doni49

I don't have time to look at your files right now but it seems obvious the jettys are causing a ripple in the triangulation. As a workaround you could try fitting the shoreline around the jettys.

Neil Wilson (a.k.a. neilw)
Infrastructure Suite/C3D 2013, LDT 2004, Power Civil v8i SS1
WIN 7 64 PRO
HP Pavillion h8xt, i7 2600, 12 GB
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psi
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psi
Posts: 5
Registered: ‎05-15-2014
Message 5 of 18 (200 Views)

Re: Two breaklines at same elevation. Large Gap between. Contour zig-zag btwn.

05-21-2014 04:10 PM in reply to: doni49
In your original post, just make the blue feature line at elevation 822.001 and the green one at elevation 821.999 and you should get the 822 contour at both. Trim them out of the Jetty grading areas so the feature lines don't interact with each other.
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doni49
Posts: 1,955
Registered: ‎12-22-2012
Message 6 of 18 (191 Views)

Re: Two breaklines at same elevation. Large Gap between. Contour zig-zag btwn.

05-21-2014 04:27 PM in reply to: psi

I'm having an impossible time trying to figure out how to get the 822 contour to split off in two directions and then re-join on the other side of the jetty.  Baiscally, I need the 822 contour to follow the bottom of the shoreline slope, hit the jetty and then follow the blue line around the lake then along the other side of the jetty back to the bottom of the shoreline slope.  AND have an 822 contour crossing in front of the jetty.

 

I know this is possilble in real life -- I'm just having trouble getting C3D to show it in plan form.  Imagine having a ditch where the top of ditch is 822 on both sides.  At both ends of the ditch, the 822 contour would split off and rejoin itself.

 

Edit:  Take a look at this please (it's about a minute long):

 

.

 

Don Ireland



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My File is too large to post or I can't post it due to privacy issues!
Distinguished Mentor
rl_jackson
Posts: 843
Registered: ‎01-20-2008
Message 7 of 18 (170 Views)

Re: Two breaklines at same elevation. Large Gap between. Contour zig-zag btwn.

05-22-2014 04:02 AM in reply to: doni49
Your TIN lines in the triangulation are too long, you need more points for this to behave correctly, look at the length of the triangulation within the lake itself, and try to replicate that, there is absolutely no way that the area can be a true elevation of 822 for the entire area just add some additional tin points and make them .01' higher or lower, and the problem will resolve itself.
C3D12-13
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jmayo
Posts: 3,002
Registered: ‎11-13-2006
Message 8 of 18 (165 Views)

Re: Two breaklines at same elevation. Large Gap between. Contour zig-zag btwn.

05-22-2014 05:17 AM in reply to: doni49

Here's my 2 cents.

 

The tin algortithms have placed the tin lines incorrectly for this model and you have a horizontal plane modeled.

 

All of the tin lines that connect from elev 822 to elv 822 need to be swapped so there is a change in z accross the tin line.

 

Since this looks like existing/base map conditions I would tend to add the plines to the surface as contour objects vs breaklines (which I prefer if needed in design) making sure to enable the options in the Minimize Flat Areas By. I do this because it is much easier and more effective for a one shot base map condition.

 

In a design situation I would add the data as breaklines and add more breaklines to fix it. Swapping edges and adding points to the tin via surface edits can bloat the surface definition often with outdated edits. The breaklines give me a definitive object to edit in the model and minimize the surface definition. 

John Mayo, PE
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jmayo
Posts: 3,002
Registered: ‎11-13-2006
Message 9 of 18 (161 Views)

Re: Two breaklines at same elevation. Large Gap between. Contour zig-zag btwn.

05-22-2014 05:22 AM in reply to: jmayo

Oh forget my 2 ceents above. I read quickly and missed the same elev on BOTH breaklines. :smileysurprised:

 

You need a high or low ridge in that area as already staed by smarter people than I. :smileywink:

 

I would go with a the breakline for the reasons I did state.

John Mayo, PE
IDSP 2014
Win 7 64, Xeon ES165@3.2Ghz,
64 GB RAM, Quadro K4000 (x2)
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jmayo
Posts: 3,002
Registered: ‎11-13-2006
Message 10 of 18 (160 Views)

Re: Two breaklines at same elevation. Large Gap between. Contour zig-zag btwn.

05-22-2014 05:25 AM in reply to: jmayo

... hmmm

 

I might simply try changing the elevation of the 822 breakline I do not want a contour on to something other than 822. 821.999 or 822.001

John Mayo, PE
IDSP 2014
Win 7 64, Xeon ES165@3.2Ghz,
64 GB RAM, Quadro K4000 (x2)
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