AutoCAD Civil 3D General Discussion

AutoCAD Civil 3D General Discussion

Valued Contributor
61 Posts
1 Kudo
Registered: ‎08-07-2012
Post 1 of 4

My 2D polylines are acting wierd.

232 Views, 3 Replies
04-29-2013 05:09 AM



I attached a picture where you can see my problem. The outer polyline is what i wanted to offset. As you can see, it did offset, but only partially.
It has to be the same problem i have with my grading. I graded a featureline to a certain elevation (29,50). I would expect a nice smooth contour as the 29,50 elevation, but what i got is displayed on the second attachment. All the unparallel lines are 29,50 countours and make a flat surface.

Has anybody got an diea what causes this?

*Expert Elite*
2,537 Posts
267 Kudos
Registered: ‎05-21-2008
Post 2 of 4

Re: My 2D polylines are acting wierd.

04-29-2013 06:12 AM in reply to: karlkarpuk
I suspect these two problems are not related.

If you turn on the display of Surface Points and Triangles it will help you to see what is causing the contours to be as they are.

Credit where credit is due! Give kudos or accept as solution whenever you can.

13 Posts
0 Kudos
Registered: ‎04-04-2012
Post 3 of 4

Re: My 2D polylines are acting wierd.

05-02-2013 02:18 PM in reply to: karlkarpuk

The grading issue has to do with the triangles and points.  CAD is probably automatically minimizing flat areas on surfaces, so it will be adding random points in the middle of your single contour.  You can go to the edits section of your surface in prospector and delete this edit and it may help.

If it doesn't fix it try "adding lines" and "swapping edges" from the same surface edit menu in the prospector, or from the edit surface ribbon button.  For some reason CAD reads between certain points that don't make any sense. This may take some time to get a hang of but should ultimately fix your grading problem.


As with the above post, I'm pretty sure the polyline issue is unrelated, but I'm not sure I can help with that

Valued Mentor
473 Posts
42 Kudos
Registered: ‎09-23-2008
Post 4 of 4

Re: My 2D polylines are acting wierd.

05-03-2013 11:01 AM in reply to: karlkarpuk

A simple way to fix the display of your grading contours is to grade to an elevation just past your real target - like elevation 29.501. Then you will get the flatness that C3D hates out of the range of your 29.5 contour.

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