OBJ exported from mesh has holes and no volume according to Fusion 360

Hi All-

I am trying to import meshes that were produced using CSG operations then exported as OBJ into Fusion 360. They look fine but I can’t do anything with them because Fusion thinks that they are not closed volumes.

Here’s a simplified example:

Any idea what’s going on here?



Hello! Unfortunately CSG is susceptible to messing up normals, which would cause the detection as holes. Does recalculating the normals helps? https://playground.babylonjs.com/#IW8TYF#3

Sadly, it does not.

Thank you for the information, though.

I figured out how to fix this problem but the solution isn’t reassuring because I don’t understand it.

BTW: The problem is not strictly about CSG operations messing up normals. A simple box has the same issue when imported into Fusion 360.

The solution is to “wrap” the solid in Fusion 360.

(I understand this is probably off-topic but I hope someone will find it useful)

By wrap I think what they are doing is recalculating normals on facets that share 2 common points. Any ideas as to why this would be necessary?

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