Railing hosted to topo does not work in one area

[mpukas]

I'm creating a fence by using a railing hosted to a topo in Revit 2020. In one part of the topo, the railing blows up and does work. I can drag the railing all around the topo, and it conforms nicely to the various slopes, except in one area. As soon as it gets past some arbitrary, mysterious point, the railing just gets funked up. It's an almost flat part of the site. I've edited the topo and there are no errant points. The topo surface is not split and does not have any subregions. The attached screen shot shows one railing that sits on the topo as it should, and one just past the point where it gets funked up. I'm at a loss on this one... just another day wasting time trying to de-funk Revit's inconsistencies... 

[barthbradley]

The Rail is overhanging the Toposurface. Just edit the Rail to remove the overhang.  Hosts to Toposurface just fine after doing that.  

[mpukas]

No, that's not the problem. I can drag the railing to overhang the topo and it will still conform to the topo surface just fine. It's just one isolated area where the railing misbehaves... 

[mpukas · Accepted solution]

...and I found the problem, with help of an excellent tech support from my reseller, Applied Software. The area of the topo where the fence was misbehaving did not have any points. I placed a few points in the vacant area, and the fence now behaves normally. 

[barthbradley]

Ah, I see what you were talking about now!  That's a wicked cool solution.  More Points. Thanks! I'll remember that one.  

...I'll call it the "mpukas workaround".  

[mpukas]

It's just another one one of those endless Revit quirks that no program developer ever thinks could be possible until an end user encounters it in a unique situation. Just another Revit hack that the developers will probably glance over and say "eh, there's a work around, good enough".  I probably spent 3+ hours trying to trouble shoot this one, including remote access w/ tech support... I doubt Autodesk will reimburse me for time lost... 

[rkelleyPKW7G]

I cannot believe this was the culprit! Thank you SO much! Fixed all of my railings by adding a point or two to the topo.

[mhiserZFHXS]

This just saved me a good bit of frustration in R23. Thanks.

[mcmonagled]

Still happens in 2024 with toposolids. 
Adding a couple of points on the surface fixed it.
Weird it only affects plans for me, 3d views are ok.