brep structure of cylinder

Technical discussions
Sergio Trastevere
Posts: 2
Joined: Wed Sep 04, 2019 4:31 am

brep structure of cylinder

Postby Sergio Trastevere » Wed Sep 04, 2019 4:38 am

Hello

I have loaded a .brep file I created in opencascade - based application. Particularly brep structure seems to be different on open cylinders (non-solid shell with a single face). The old app shows a single wire but in dg kernel I am getting two wires.

Can anybody shed a light on this please?
Thanks

nickz
Site Admin
Posts: 198
Joined: Fri Jul 26, 2013 3:58 am

Re: brep structure of cylinder

Postby nickz » Thu Sep 05, 2019 7:14 am

Hello Sergio
DGK removes seam edges from the cylinder's faces on load. It is the way we do it. This should not create any problems. Seam edges are unnatural, unnecessary and confusing in our view.

Seam edges are the two geometrically coinciding edges going in opposite direction. They are added by some software to make cylindrical surface a rectangular curved patch joined by two edges (seams) to form closed surface. This way the face has a single wire with four edges.

DGK goes another way, used by many software also: We model it as a single face with two isolated wires with a single edge in each.

As you know, surface in BRep can be represented in many ways. It is similar to mesh. Same surface can be meshed in various ways

Regards

Sergio Trastevere
Posts: 2
Joined: Wed Sep 04, 2019 4:31 am

Re: brep structure of cylinder

Postby Sergio Trastevere » Fri Sep 06, 2019 1:02 am

Thank you, Nick


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