Joining surfaces into non-manifold B-rep

I’m trying to generate a simple wing box geometry with ribs for shell meshing. I’ve generated the surfaces and am trying to join them into a single non-manifold B-rep by using the Brep Join component. However, I get 3 B-reps instead: the inner and outer sections (open B-reps), and the rib (a trimmed surface). Meshing this then gives me 3 disconnected meshes that have edge nodes which do not line up with each other.

I’ve already tried playing around with the tolerance. I’ve also tried joining the 3 meshes and then welding them to no effect.

Is there a way to join the surfaces together?

Hi @hkit.yong,

If you bake your geometry to Rhino and then run NonmanifoldMerge, do you get the result you are looking for?

– Dale

Hello @dale,

I’ve just tried NonmanifoldMerge and it did give me a single B-rep. However, when I linked it back into GH and passed it into a Mesh parameter component followed by Quad Remesh, the resulting mesh was distorted.

I’m not sure if I should be post-processing the merged B-rep in some way. I’ve included the unmerged B-reps for reference.

wingbox.3dm (104.3 KB)

Hi @hkit.yong,

The NonmanifoldMerge command creates a non-manifold Brep from intersecting surfaces and polysurfaces. This generally only useful for export to analysis programs and can cause normal Rhino operations on these objects to fail.

Given this, why do you want to create a non-manifold Brep? That is, if you are just going to quad-mesh the Brep, why bother?

– Dale

Hello @dale

The non-manifold B-rep is the outcome of joining the three smaller B-reps. The edges of the rib is shared among three faces. If I just quad-meshed the smaller B-reps without joining them together, the resulting meshes are not connected and hence are not structurally accurate.


Did you find the solution?