Hi Gerrit,
On 04/03/2010 01:57 AM, Gerrit Voß wrote:
>
> hmm, sounds more like both of you remembering gdal (which is for
> geospatial data). I put gdal support into an image loader. CGAL I
> can't remember seeing and definitely did not touch myself.
Ack! You're right, that's what it was. :(
Sorry about the confusion. So right now there is no CGAL support in OpenSG.
However, if somebody wants to add it, there are three ways to do it.
One is to just write a CGAL -> Geometry converter.
Pro:
- quick and easy to do
Con:
- duplicates memory
- need to be completely updated anytime anything changes
Two is to write a CGALCore that keeps the CGAL structures inside and renders
directly to OpenGL from them.
Pro:
- No overhead
Con:
- Performance might be suboptimal, as it might have to be immediate mode(not
sure how CGAL arranges its data)
- Non-trivial. CGAL (like many geometry libs) likes to use templates a lot to
give freedom of what to store. But templates FieldContainers are not a trivial
thing. We only do it in very few places (the GeoProperties are the only ones
that come to mind), and there is a good amount of low-level hacking involved in
making it work.
Three is to do two but use the CGAL structure directly for rendering as much as
possible.
Pro:
- Little if any overhead
- Better performance than 2
Con:
- All complications of two plus some more
So if the primary goal is to generate some geometry and render it using OpenSG
number one should be fine, as long it doesn't change too often. For dynamic
geometry two or three are the way to go, but they're both non-trivial. There
was
some support for that in OpenMesh, but it did limit the OpenMesh guys a bit in
what they could do, so they abandoned it.
Yours
Dirk
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