Closed open polysurface which openings dont have closed, planar loops of edges


After triming a closed polysurface with another closed polysurface, I get one closed and one open polysurface. I would like to make a booleen union on them to have only one closed polysurface, but it fails due (I guess) to the open polysurface. Is there a way to get to this final closed polysurface? Perhaps if I could close this open polysurface, the booleen union will work, but how could I do this?

Thank you very much :slight_smile:

Can you post the surfaces/polysurfaces in question? Easier to explain with an example.

Thank you for your replay @Helvetosaur!

Of course, attached is the file.
In this file there is 4 main figure which represent the following:

  1. the one on the left is the initial model I made
  2. the one next to it is the model once I tried to make it one closed solid (but did not achieve)
  3. then, its the example I spoke about, which might help me to fix 2).
  4. finally, the one on the right is the results of the example I spoke. In other words, when I trim these two initialy closed polysurface (cf 3)), then I gent one closed and one open polysurface (see 4)). Moreover, with the showedge commande I have now some naked edged :(.

Any tips/help will be highly appreciated, thank you so much for your time.

model-quesiton.3dm (6.6 MB)

I copied 3 and used the command BooleanUnion. The result is a closed polysurface. model-quesitonDC1.3dm (310.4 KB)

I can duplicate your 4 using a single Trim operation. The results are as expected using Trim.

BooleanUnion of the objects in 1 fails because of the parallel cylinders which just touch along lines. Boolean operations in Rhino usually don’t work with objects which touch along lines or curves.

Thank you very much for all these information @davidcockey.

I indeed woul dlike a closed polysurface as mentioned in your first sentence, but without the small part of the bigger polysurface (cf my number 4). In otherwords can not make 4) a closed polysurface by triming and then booleen union on the result.

COcnerning your last paragraph, this is very interesting! So it means, that we can not have a closed polysurface composed of objects that are just touching? I used offset multiple command with the distance beeing teh exact circle diameter which I used the to sweep around each of those. If I understood correctly I should do offset multiple but using a smaller distance between each object than the size of the future ‘sweep objet’?

BooleanUnion worked for me to create a single closed polysurface from the two objects in 4,

You can have two closed polysurfaces which happen to touch along a line or curve, but you can not combine them into a single closed polysurface. Move the surfaces so that they overlap by a small amount and you can create a single closed polysurface.

Thank you again for all your help @davidcockey
1 paragraph: Indeed, it now works for me as well… its so strange, I tried it so many time before!

2 paragraph: I can imagine that if I was trying to make a closed polysurface only with these two cylinder that touch only throudh a line. But, in my case their is a structure (closed polysurface) on which all these objects are on it. So, even in that they can not be in the same final closed polysurface juste beacause the touch through a line? I really dont understand…