Re: [brlcad-users] Storing custom data per point_t and BRL-CAD primitives

[Alex D. <nu...@gm...>]

Dear Sean,

thank you for this detailed reply. I skipped it somehow.
These days I hope I'll have some time to look at the options and come back.

In the last part of my master's thesis, as much as time allows, I should 
modify BRL-CAD to add some features needed by the sponsor, mostly public 
code.

Best wishes,
:) Alex

Christopher Sean Morrison wrote:
> Hi Alex,
>
> There are a few options that come to mind:
>
> a) If it's not performance intensive metadata, you can associate  
> arbitrary data to any object as an attribute or set of attributes.   
> Attributes are key=value string data.  You could utilize that to  
> store per-vertex metadata using either keys that tie to vertices or a  
> single key that ties to a value set for all your vertices.
>
> b) You could maintain a parallel storage of arbitrary binary data  
> using binary objects.  I'd probably set an attribute (e.g.,  
> color_values="my_table") on your NMG object that refers to a binary  
> object.  The binary object ("my_table" in this example) would then  
> contain whatever data you want.
>
> c) We could extend any one of the NMG structures (e.g. struct vertex)  
> to have a user data pointer.  Simple enough, though if this route is  
> selected, it'll probably be worthwhile to add a user data pointer to  
> *all* of the core NMG structures (vertex, edge, loop, face, shell,  
> nmgregion, and model) or their respective use structures for  
> consistency.
>
> d) You can utilize the nmg_visit_handlers interface to maintain an  
> arbitrary data structure with your data when it actually comes time  
> to process the data.  This is probably the most effective for in- 
> memory processing, but of course is not that effective as a means of  
> serialization (though coupled with (b) it could be).
>
> If (c) is most appealing, we can discuss in further detail on the  
> brlcad-devel list to make sure any change we make fits your needs.   
> There are possibly a few other options as well, but that's just what  
> immediately came to mind.
>
> Cheers!
> Sean
>
>
>
> On Apr 27, 2009, at 8:28 AM, Nu Eu wrote:
>
>   
>> Hi,
>> I would like to be able to store custom data for some vertices from
>> BRL-CAD object and don't see any means to do it after reading the
>> introduction.
>>
>> The next thing I thought of is adding some structure to the base
>> vertex type. But point_t is a vector of floats, so it would be quite
>> complicated.
>>
>> What else could I use to store custom data?
>>
>> Thank you for attention,
>> Alex
>>
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>
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