2013/10/31 Christopher Sean Morrison <[email protected]>:
> On Oct 31, 2013, at 04:30 AM, Daniel Roßberg <[email protected]>
> wrote:
>
>> 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.
>
>
> Fair point. I've said for years that our emphasis is on "solid modeling"
> (i.e., 3D) and not drafting features but even our closest counterpart solid
> modeling systems (like Solidworks) do indeed also support 2D entities and
> techniques (they're not sometimes not very good at them, or they've been
> retrofitted). Looking back through old presentations on NMG recently, that
> was even part of NMG's original design where the n-Manifold is explicitly
> describe in terms of 3-manifolds, 2-, 1-, and even 0-manifolds (non-manifold
> geometry, e.g., a point).
>
> This raises an interesting issue about shotline behavior, but it's not much
> different from non-closed sketch or non-volume nurbs. We either ignore them
> or treat them as a 0-thickness thin surface.
Exactly. Points and lines are not part of the 3D model but of the
design(-process). They could mark the extends, symmetries etc. of the
model. Then the solids can be fitted along these
(intersection-)points and lines. The points and lines itself will
never see the light.
2D surfaces are a little bit different. They could be part of the
design if e.g. objects are mirrored through them. Or they could be a
place-holder for objects not modeled in 3D, a background with hills
and trees for example. A 0-thickness thin surface would be an
adequate ray-trace hit here.
Regards,
Daniel
------------------------------------------------------------------------------
Android is increasing in popularity, but the open development platform that
developers love is also attractive to malware creators. Download this white
paper to learn more about secure code signing practices that can help keep
Android apps secure.
http://pubads.g.doubleclick.net/gampad/clk?id=65839951&iu=/4140/ostg.clktrk
_______________________________________________
BRL-CAD Developer mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/brlcad-devel
