missing faces when importing step file


I was trying to import the attached file and I noticed that it is missing the top Sphere when imported using OpenCascade, Same geometry opens fine in other CAD Applications.

Any suggestions for fixing this will be appreciated.



PG's picture

The STEP file is created in which CAD system ?

Ashraf's picture

PG the file was create with Alibre

Roman Lygin's picture

It's not that the top surface is missing. It is that Open CASCADE selects wrong path of the sphere (let's say bottom vs top) - see enclosed image.
The root-cause is that the face boundary is defined as a single circle and OCC was confused which part of the surface to choose. Should there be extra information (like seam-edge or a pole/degenerated edge) it would figure it out. It can be either that the file itself contains wrong orientation of the boundary or OCC made a mistake, did not investigate further.

Does not help much, but should hopefully give you some clue anyway...
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Ashraf's picture

Hello Roman,

Thanks for the explination, this makes perfect since, so open cascade got the wrong side of the sphere.

I recive a good number of STEP files, and most of the problems I have is with files generatd with Alibre.

for example the attached file crashes OpenCascade