Solid mesh from brep creation problem

Grasshopper
1

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?

rib vault
rib vault1333×750 426 KB

archicad
archicad1054×948 80.7 KB

2

any advice on this?

3

3. Attach minimal versions of all the relevant files

4

vaulted_ceiling_2019Dec16a
vaulted_ceiling_2019Dec16a1348×401 46.2 KB

vaulted_ceiling_2019Dec16a.gh (19.3 KB)

P.S. Purple group.

vaulted_ceiling_2019Dec16b
vaulted_ceiling_2019Dec16b1142×572 93.4 KB

vaulted_ceiling_2019Dec16b.gh (18.1 KB)

P.P.S.

vaulted_ceiling_2019Dec16b2
vaulted_ceiling_2019Dec16b21341×480 57.9 KB

2 Likes
5

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?
keresztbolt.gh (51.3 KB)

6

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!

rats_nest
rats_nest741×519 46.4 KB

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?

keresztbolt
keresztbolt1068×372 42 KB

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

closed
closed1000×633 45.5 KB

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

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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…

10

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

11

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

image
image1014×730 267 KB

So as a conclusion it seems more related to Archicad.

12

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” .

vaulted_ceiling_2019Dec21a
vaulted_ceiling_2019Dec21a715×242 9.95 KB

vaulted_ceiling_2019Dec21a.gh (16.0 KB)

13

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

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