its from clockwork, im wondering if theres an alternative method to do the same thing. Something more reliable or stable. I think maybe the complication of the topo makes it crap out some times, but im just guessing.
Topography.IntersectionWithPlane
Hi @vanman
It may be that the intersection points attained by the node are being sorted into an order that initiates the āPolycurve Curves my not be branchingā error (I have dissected the node and its functions, and this appears to be the case) Can you post a screen capture of the topography? and where the intersect plan occurs?
The below capture indicates the sorting for the polycurve intersection is more complex than it need beā¦
(This is the insides of the Mesh.Intersection with Plane node)
Hi Ewan,
Will do my best to respond to what your saying, sorry if theres some confusion
The topography doesnāt show up in Dynamo as it usually would after running the script. below is what it looks like in revit. No matter where i cut a section or elevation in it the node wont work as it usually would. It does run for a long time before getting the error though
Have you modified the Mesh.Intersection with Plane node and i should change it and give it a go your way? My node looks like this when you go into it from the package.
I extracted the nodes from within into a blank DYN, to determine where any error was occuring.
Can you post your current DYN and a stripped version of the file?
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I see, smart. I was wondering if dynamo had some sort of live progress function you could watch with.
Here is the dyn and revit file with topo.
Topography.rvt (2.3 MB)
Existing Ground Lines_For Current View.dyn (10.3 KB)
When the DYN is executed in a Section view (that cuts the topography) it does find points along the surface, it just cannot create the Polycurve because of the ābranchingā effect of the point order being jumbled. This could be due to the roughness of the surface.
You can work around this by using the extracted points the node does find, cleaning them and sorting them along a vector, before constructing a Polycurve. Worked for me, hope it does for you 
Awesome! what package is the node āsort points by average vectorā from?
The Sastrugi Package 
What happens if you remove the List.FirstItem node that is after the Pick node?
Also where is your section taken in relation to the topography? Can you show a plan view?
(I am not sure the file you uploaded contained the same section you display in your examples, but correct me if im wrong)
Same deal without that node. Sorry you are correct I just opened a new file and copied the topo through to make it small enough to upload here. Topo in the original purged file is Below. The section view I just tried is āSection A1ā under group āA Building Consentā. All the sections and elevations dont seem to work though for me
Thanks for the new file, will try it in the morning 
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I have run the DYN with the exact same inputs and have this result.
A few things to try.
Does adjusting your view depth to be say 100mm make any difference?
Update Clockwork? What version of Clockwork do you have installed?
Iām running 1.31.0 at the moment.
Try this DYN which I have extracted the node contents out of Topography.IntersectionWithPlane.
It displays that there could be some lacing issues and null values stopping the creation of the Polycurve.
(This has, with some tweaks, created a polycurve on the topography, as seen in the background preview)
Existing Ground Lines_For Current View TWEAK.dyn (47.4 KB)
Apart from trying the above, I may be at a loss with this one @vanman 
Hi Ewan, thanks for all the help and replies so far! Soā¦
Adjusting view depth made no difference.
Iām running clockwork 1.0.3 (will update this and try again)
I was using your tweaked version but one of the nodes you created appears to be broken. Not sure how to type an input with a hyperlinked input after. I say hyperlink but I donāt know the terminology for it with dynamo or programming
Tried the alternative method you kindly created but that unfortunately errors my revit and closes it
Geometry working range maybe?
So this worked! Just skipped the node i was unsure about. Iām going to go back and try some of your other suggestions with updated clockwork
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Iām trying to use your solution across multiple views. Think Iām close but cant get it right with the lacing i think. It drew lines across 3 views but only the 3rd view had the lines in the correct place. The things I have done to modify so far are below.
I by passed the plane node because it didnāt list multiple plans and i changed geometry.intersect from cross product to longest lacing. Iām not sure if that was an error to do but it got it drawing lines across multiple views.
I changed the lacing on the DetailLine.FromCurve to longest as well
Any suggestions to get it drawing the lines correct across any amount of selected views? 
Existing Ground Lines_For Selected Views_Test.dyn (73.2 KB)
an updateā¦ it dosnt seem to like having selected views on different planes. Something Iām probably missing earlier on in the script. The first two views are on the same plane and it gives nulls. The other two are on another plane and it puts threw the values. Probably isnāt even related but thought id try give it a go
Have you tried my alternative workflow? It might be simpler with respect to lacing and multiple views. If you gather your view planes in one list then connect that to the Mesh.Intersection node I canāt see why it wouldnāt work (canāt test that till tmw) Can you install the MeshToolkit package?
I gave the alternative work flow a go but it crashes my revit unfortunately