[MOAB-dev] ReadCGM question

[Jason Kraftcheck]

On 11/03/2010 03:59 PM, Steve Jackson wrote:
> 
> On Nov 3, 2010, at 15:53 , Jason Kraftcheck wrote:
> 
>> On 11/03/2010 03:43 PM, Steve Jackson wrote:
>> 
>>> 
>>> * I think it would it be more correct to replace GEOMETRY_RESABS
>>> with faceting_tol, i.e. the tolerance value that was used in calling 
>>> edge->get_graphics().  Does anyone disagree?
>> 
>> Perhaps you could change it to be the merge tolerance.  Merging is 
>> (hopefully) the source of such warnings.
> 
> You anticipated my next question, which was why this error was happening.
> (I.e. do I blame the geometry, or blame the faceting engine?)

My guess was the geometry, because I don't see how or why the faceting
engine would introduce such an issue (other than a plain old bug.)

> I don't
> know of a way to get at the merge tolerance from the context of the
> error, since merging is done to a geometry before ReadCGM gets access to

After thinking about it for a bit I think my suggestion of using the merge
tolerance was a poor one because Cubit only ever tracks (AFAIK) the merge
tolerance that it will use for future merges.  What you'd actually need is
the merge tolerance what was enforced during the merge of each entity (or
whether a 'forced' merge was done, which would have bypassed tolerance checks.)

> it.  But perhaps when this error is prevalent, it suggests that the
> geometry was created with a bad choice of merging tolerance? ~S
> 

It suggests that perhaps that GEOMETRY_RESABS doesn't accurately reflect the
user's idea of what constitutes equivalence.  And emphasizes the fact that
cubit is somewhat inconsistent in that regard (default merge tolerance is
greater than GEOMETRY_RESABS).

- jason