Zhao,
sorry for the late reply. I haven't my SourceForge password with me
and won't be in my office the next days (Easter, you know). Therefore
I reply via the mailing list.
The BRL-CAD combinations (regions and groups) are much more powerful
than the model and nmgregion. You can simply substitute model and
nmgregion by groups to preserve the look but with regions and the
other boolean operations we have more features available.
Furthermore, reducing the NMG to the shells would support the BRL-CAD
philosophy to have simple structured primitives and to do the higher
structure consistently with combinations, where we have groups,
regions, boolean operations etc..
This means, that all NMG primitive functions have to be
changed/removed to just leave the shell(only one shell) as the top
struct Other, not in src/librt/primitives/nmg functions, which have
now an NMG as input or output, may need to be changed to a combination
as input or output. It depends.
Improvements to the NMG shell primitive are welcome. This will
hopefully be the main part of your GSoC work ;)
Regards,
Daniel
---------- Forwarded message ----------
From: Zhao Anqing <[email protected]>
Date: 2014-04-12 9:57 GMT+02:00
Subject: [brlcad:patches] #263 Convert NMG Model to BOT
To: "[brlcad:patches]" <[email protected]>
Hi, Daniel
Thanks for your patient explanation which makes me gain a deeper
understanding of the reason for removing this two struct.^-^
I hope to consult you some more details about NMG parts in BRL-CAD. If
I haven't made a mistake here, a model with several regions is usually
used to deal with detached body; a region with several shells is used
to deal with kinds of hollow situation. So, after removing the two
structs, *.g file and BRL-CAD region as the substitute could achieve
the same function perfectly?
That means, all functions will be changed/removed, just leave the
shell(only one shell) as the top struct of NMG part?
And, according to my professor's opinion, Weiler's paper published in
1980s is maybe a bit obsolete. I am familiar with ACIS's data
structure which selectively absorbed the advantages of Weiler's work,
and it can represent non-manifold well. Using so much XXXUse structure
rather than only splitting edge into edgeuses may make things
complicated.
Thanks.
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