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Regular Contributor
Posts: 58
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Accepted Solution

face with negative area

Hello,

 

Is there a common reason for an error "face with negative area"? It was introduced by api_cover_circuits. I checked the face normal, coedges orientation, partner coedges orientation - everything looks fine, but ACIS check produces:

 

Insanity: face with negative area
Insanity severity: 0 -> ERROR: issue is an error.
Insanity subcategory: No sub category
Insanity details: ( area = -0.089738236043, relaccy = -1.000000000000 )

 

Thank you!

 

Spatial Employee
Posts: 151
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Re: face with negative area

Hi YT

 

Often faces with negative area are sliver faces.  To define the face area, ACIS sets up an integral of dA (the area element) over the UV parameters for the face.  If the boundaries are bad (self intersecting), or the orientation is backwards, you can get a negative area face.  It is a bug for an ACIS API to make faces like this.  You may want to log it with support.

 

cheers

 

Eric Zenk

Regular Contributor
Posts: 58
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Re: face with negative area

Thanks Eric,

Yes - I'll report it as a bug.

The face looks perfect, not self-int., not sliver.

Backward orientation... It's not quite clear what to look here for: face's sense, coedges orientation, ...?

Thanks again!

Regular Contributor
Posts: 94
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Re: face with negative area

Can you also give us an example here ?

Regular Contributor
Posts: 58
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Re: face with negative area

This is accepted as a bug by Spatial.

This only happens if a covering surface is provided by a client (at least I did not see any other cases).

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Regular Contributor
Posts: 58
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Re: face with negative area

See also api_check_face_loops