Merge several surfaces ( from polysurface) in one signe surface

Hello ,


I need to have a clean single surface for after meshing it for conputational fluid simulation.
Here a picture to have a overview,

I exploded a polysurface ( double curvature) in more than 14000 single surface. ( “A” on my pic)
Using : _MergeSrf I can join them 2 by 2. ( “B” on my pic)

Using a lot of _MergeSrf adding each individual element, I can finally merge a bigger part ( “C” on my pic)

But I can not do that for all my file.
the command _MergeAllFaces do not success ( as said in the doc : co-planar polysurface only)

Is there a comand which do that ?
A way using GH ?

Many thanks
Have a nice day


Hi Fred - I don’t see a clean way to do that - a messy way might be this:

  • Join all the surfaces.
  • Make sure isocurves are not displayed for the results.
  • ExtractWireframe
  • Then SelChain and Join to get the individual long curves in each direction.
  • NetowrkSrf.


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other option could be using _Patch
Extract the vertices first

then you can project curves to get the smooth edges for resurfacing

Hi Pascal ,
Thanks for your reply.

I think i understood your strategy. But my problem is SelChain ask me at each junction which curve to select , so it heavier then doing it by hand.

Please find below a more zoom out view of my problem (airfoil)

and a view when I use Selchain , i’am missing smething ?

If it can help the 3dm file attached ( zipped): (13.5 MB)

Hi Diego Krause,
Thanks also for your proposal , unfortunatly _Patch is making a surface too different from the original one.

Thanks all
Have a nice day

Hi Fred - set chain continuity to Tangent, not Position. Any better?


Hi Pascal ,
no it doesn’t work at all with tangent. only position.

Hi Fred - set a high angle tolerance on Tangent - like 45 - that way it will ignore the 90 degree corners and just track along the ‘correct’ direction.

But I see this is a faceted thing, not smooth - you may want to use CurveThroughPolyline once you have all the segments joined.

@fred3 - see the attathed. I only did a segment…
airfoil_poysurface_forum_partly.3dm (5.5 MB)

Joined the curves (SelChain) and since some are arcs, I changed the degree to 1 and then SimplifyCrv to get polylines, then CurveThroughPolyline and NetworkSrf.


1 Like

Ok I got it , thanks a lot for the exemple file.

many thanks for your time
Have a nice day.