Solid mesh from brep creation problem

I am trying to put together a parametric roman rib vault in Grasshopper to be used in BIM (ArchiCAD).
First I construct the surface and then I add the side surfaces and finally I am adding the top surface and join all the breps, which results in a closed brep according to Grasshopper. After this I am using the brep to mesh component. The problem is when I am importing into BIM app and trying to make a section, it appears not to be solid. It has to be solid to make a nice proper section. Any suggestion for a better process?

any advice on this?

3. Attach minimal versions of all the relevant files (19.3 KB)

P.S. Purple group. (18.1 KB)



Hi Joseph,
Thanks very much for your solution. Actually the archs have different height in my case. But actually I am interseted in the theory. Why is my closed brep not solid? As I said somewhere I have read that in Grasshopper closed breps automatically considered solid, but not in my case. What do I do wrong? (51.3 KB)

Ugh. That’s not how the Romans did it, did they? I can see several reasons your model fails to create a “Closed Brep”. The four bottom corners taper to nothing. The top inside touches the top outside. I might have looked a little deeper but one look at this code and I want to close the file and run away!

P.S. At the far right edge of your model there is a pair of Dispatch components connected to a Merge. The ‘D2’ input appears to be the “Closed Brep” you want?

I dont undestand why are you saying it not closed. Grasshopper says it is closed.
See attacehd image.

I said it is a “Closed Brep”, as shown in the image I posted. Why aren’t you using it?

See the very first image I have made in ArchiCAD. If it was really closed the model would be solid isnt it?
Maybe it is a bug in Grasshopper…

any idea that a closed brep supposed to be solid or not?

I may be wrong but there is no real solid in Rhinoceros. It is not a solid modeler. Rhino use BREP representation so Boundaries, if there is no “free” edges the surface is considered closed.
I don’t know Archicad, but what uses this software uses ? Mesh or Brep ?
If Mesh Joseph gave you clean mesh that are closed (all edges connected to 2 faces).
Clipping plane in Rhino works well with @Joseph_Oster meshes and Brep

So as a conclusion it seems more related to Archicad.

The “Closed Brep” in @Balazs’ model is sketchy because the four bottom corners taper to zero thickness, which won’t behave well as a “solid” . (16.0 KB)

Are you really sure it is not soild modeller despite Grashopper has dedicated solid operation commands, like boolean difference, etc…?

It is not my model. Is there way in grasshopper (maybe a dedicated command) to check that the model is watertight (solid) ?