Can't create polygons.Some links could be lost

[Gyula_58]

Hi,

There are two polygon topologies in the dwg attached. The 'Parcels' topology is a source while the 'RoW'  topology represents an overlay topology. Both are reported correct and complete, nevertheless an intersection overlay operation

does not show the expected result. Instead, a rather painful error message comes up: Can't create polygons.Some links could be lost. Frankly, I have never known any of the messages before...

How can this happen? The input topologies are OK. What am I doing wrong?

Ironically, this sample is a part of a greater drawing and the rest of the topologies work just fine.

If somebody could point me in the right direction, I'd be very very grateful.

Thnx.

Gyula

<Civil 3D 2009>

[Alfred.NESWADBA]

Hi,

I could reproduce the issue with your drawing. However when I create a polygon topology I always run the _MAPCLEAN with the option to convert all to polylines and also to connect the elemens on pseudonodes (sorry that I don't know the exact word for this in the _MAPCLEAN dialog in english). I did that for both of your topologies, then recreated them and ... it works now.

I have to add: I used Civil3D 2010 and not Cviil3D 2009 now, but I gues the result will be the same.

HTH, - alfred -

[antoniovinci]

Upon _MAPCLEANing, there's another option not to forget, before creating a topology: "Break crossing object".

[Alfred.NESWADBA]

Hi,

>> there's another option not to forget, before creating a topology: "Break crossing object"

Just to make sure for readers coming up later to this thread: that option is only obligatory for polygonal topologies (and as the OP has already got the topologies created he had no crossing geometry).

For line-topology it can make sense to not activate the "break crossing object", e.g. for a street routing system when you have crossing streets that are not connected (bridge).

- alfred -

[antoniovinci]

In Ordnung, liebe Herr und... Gruess Gott !

[Gyula_58 · Accepted solution]

Hi Alfred,

Thank you for answering my question. I really appreciate your suggestion but unfortunatelly I have to insist on keeping my own rules: a link is a line entity. Otherwise the command you did not know in English: dissolve pseudo nodes.

Finally, I believe, I managed to find a workaround of the issue. Not too elegant though, but it seems to me the overlaying algorithm is sensitive to the layout of the geometric elements in the topology. One of the nodes  was moved by 0.01 du and some links were added to the overlay topology and this solved the problem. Maybe I am mistaken, but I have been playing with this for a while and  I am fed up with it. Anyway, if somebody has more logical idea (maybe at AutoDesk), please do not hesitate to tell it to the public.

Thanx,

Gyula