[cgma-dev] Observer question?

[Tim Tautges]

On 07/22/2013 11:01 AM, David Thompson wrote:
> Hi Tim,
>
>> Good hearing from you, when did you leave Sandia?
>
> It's been about a year.
>
>> On the observer question, entities that are not intersected will persist, including the RefEntity's, though whether
>> something isn't modified depends on what the engine does (it's keyed off whether the underlying engine changes its
>> topological entity).  With Cubit, we've had mostly expected results that way, so no big worries.
>
> Any idea about the OCC backend? I ask because the attached program calls webcut on one of the example models
> (62_shaver1.brep) and faces to both sides of the cut sheet (as well as one that intersects the sheet) all report
> GEOMETRY_TOPOLOGY_MODIFIED.
>

Hmm, I haven't worked much with the OCC backend, so I couldn't say.  I'm cc'ing Jane Hu, who developed that backend, she 
might know.

> The notify_observer() method called on observers doesn't appear to provide information about the entity(-ies)
> replacing those being modified. Is there a way to obtain the resulting split or merged entities? If I create an
> attribute to hold an ID on faces or edges of interest, how fast will lookup be?
>

If it's anything like ACIS, you generally don't know the correspondence between an entity that gets deleted and the ones 
used to replace it.  IIRC you don't get many notifications of split or merge type, only of delete type (and implicitly 
create type, which show up as not having associated CGM entities yet).

- tim

> Thanks, David
>

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              Tim Tautges            Argonne National Laboratory
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