On Thu, Nov 13, 2008 at 11:49 AM, Benjamin Kirk <[EMAIL PROTECTED]>
wrote:
>>> There is actually a commented-out section of code in MeshCommunication
that
>>> used to do this using bounding spheres, but I think for my meshes with
>>> boundary-layers that would just have an annoying amount of false
positives.
>>
>> What about boundary layers that aren't aligned with a coordinate axis?
>> Won't that have nearly the same problem?
>
> Yeah, nearly the same problem...
>
>> Clearly you ought to be working on a BoundingConvexHull class. The
>> standard algorithm for polygons is on page 898 of
>> Cormen/Leiserson/Rivest; I'm sure you won't have any problem extending
>> it to polyhedra and writing an intersection test.
>
> Not sure about that, I'd say 'clearly I should get the nemesis part
> finished' and then implement what you describe. Right now we can get a
> bounding box for two processors easily enough, and (I am sure you are
gonna
> love this...) overload '&&' to return true if they intersect.
>
> Going forward, Qhull (http://www.qhull.org/) looks like it will fit the
bill
> for building the convex hull, and then we just need to write an
intersection
> test... We could go so far as to derive the BoundingBox and
> BoundingConvexHull from the same base class, so that you can use either to
> perform the test.
I'm not sure about Qhull. I don't think it's had any releases since 2003.
This in itself isn't bad, but from
http://www.qhull.org/html/qh-in.htm#library, I see:
Warning: Qhull was not designed for calling from other programs. There is
> neither API nor Qhull classes. It can be done, but it takes work and head
> scratching. You will need to understand the data structures and read the
> code. Most users will find it easier to call Qhull as an external command.
>
--
John
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