Surface.ByPerimeterPoints fails for some (random?) points

Geometry
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1

Hello,

I’ve been writing a dynamo script that converts buildings from the CityGML-format to 3d-solids.
The walls of my buildings are defined by points that create a surface. I extract the points that form a surface and try to create a surface using “Surface.ByPerimeterPoints”. The script processes thousands of surfaces and almost all work without any issue but for some, seemingly random, surfaces, Dynamo throws an error.

To reproduce the issue, I’ve extracted a “faulty” surface that is created by six points:

SurfaceByPerimeterPoints_2024-09-04_02-14-59
SurfaceByPerimeterPoints_2024-09-04_02-14-591274×492 37.9 KB

I can’t see anything special with those points - the surfaces right next to this example build without any issues.

The error reads as follows:

Surface.ByPerimeterPoints failed. Unable to create polygon : API_failed -- operation unsuccessful

I’ve also attached the script in case anyone wants to take a look.
SurfaceByPerimeterPoints.dyn (9.9 KB)

I’m happy for all the help I can get! :slight_smile:

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@pumpaij

these are the input… …which error do you have?

image

image
image1081×456 42.6 KB

could be you have to extract the right points

3

Change Geometry Scaling to Large
scaling

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I recommend leaving the geometry scaling as you risk losing accuracy of shapes. Instead pull the points closer to the origin and see if that clears the issue when making the geometry.

Instead try this:

  1. Starting with the list of lists of points
  2. Take the first point out of each sublist using a List.FirstItem node
  3. Create a coordinate system using the first points
  4. Transform each sublist of points from the associated coordinate system to the origin coordinate system (CoordinateSystem.Identity() node).
  5. Build the surface from the transformed points
  6. Might as well do any other geometry manipulation at this point as well, if you’re thickening the surface to get solids, or otherwise creating content.
  7. Shift the completed geometries back to the original location by using a Geometry.Transform node the associated coordinate systems.

As you’ve got lists of lists of objects lacing and list levels will matter - @L2 list level will likely be your best friend for most of the graph.

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This is the way!
I originally ruled it out because 95% of ~350000 surfaces built without a problem but moving it closer to 0 resolved the issue.
In my approach I just moved the whole list closer to zero and found that it worked once Y-values reached <~150000 but your workflow with moving each individual surface is much neater.

Thanks for all the replys.

Edit: The forum bugs out when I try to accept the solution - I might have to try it again later.

1 Like