2013/10/22 Christopher Sean Morrison <[email protected]>:
>
> On Dec 13, 2011, at 11:44 AM, Daniel Roßberg wrote:
>
>> If the NMG is considered to obey Euler operators then the
>> sub-dimensional elements are part of its nature. This would make it
>> to a real non-manifold in contrast to an n-manifold of pure solids (as
>> I understood the meaning of the two terms).
>
> Is there any value to us (as a solid modeling system) to support non-manifold
> geometry? While mathematically interesting to me, the modeling value is
> quite dubious for all but "plate mode NMG", which we obviously don't
> currently support.
For a 3D modeler: No (or similar to the sketch primitive). For a CAD:
Definitely 100% yes. BRL-CAD is lacking 0 to 2 dimensional entities
which all CADs have. With the NMGs we in fact would have these if we
would allow all states of them.
>> Therefore, shouldn’t we consider to
>> - remove the model and nmgregion structs and make shell the basic
>> internal structure for the NMG primitive,
>
> I love this idea actually for a number of reasons. It will probably
> eliminate 100+ functions that are merely the model or region iterator. It
> certainly simplifies the scope considerably helping to make the library more
> approachable by other developers.
>
> The only problem will be that we expose model and nmgregion in numerous librt
> functions, and "shell" is a terrible name by itself. I'd propose shell
> become the 'model' terminology-wise.
I would call it "nmg" or "nmg_t" or something like this. Currently we
have a "model" which is a little bit confusing (especially because of
having a "nmgregion" but a "shell" then).
>> - fully support intuitive Euler operators and
>
> AFAIK, it does this now. Maybe a few cases missing, but there certainly are
> the majority iirc.
Really? I compared raytrace.h with release 47476 (when I wrote the
copy function). There isn't much change in the nmg_ functions since
then. But the missing Euler-functions could be caused because of the
avoidance of subdimensional states too.
Regards,
Daniel
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