RE: [Algorithms] FW: [CsMain] Scene Graphs (Open Inventor open source + Performer for Linux)

[Graham S. R. <gr...@se...>]

I don't know if you all are aware of this (but some probably are), but SGI
has released their Open Inventor scene graph engine (version 2.1 or maybe
2.2 I think) as open source, see this link:

http://oss.sgi.com/projects/inventor/

It is an extensible/programmable scene graph engine that is quite powerful.
It has a "standard" file format as well, and built-in loaders and writers
for that format. It includes some simple animation engines, but as with all
of the engine you can write your own, customized engines.

I've developed a rather extensive application using Open Inventor (the TGS
versions and SGI versions) for about 4 years now, and I consider myself an
expert. And I'd like to mention these rather large issues that exist with
Open Inventor (SGI's version at least):

1) There be bugs in SGI's version! For example, the SoCalculator animation
engine sometimes locks up and doesn't work when you write vector equations!
That engine also sometimes gets the sign wrong when multiplying terms
together. These two are fixed in (at least 2.5 and later) TGS versions.

2) The SGI version isn't really fantastic for very large models, though that
might not be too much of a problem for some games right now.

3) The TGS version will likely continue to be a commercial product for sale.
A pity (if you want it for free) since it has many enhancements, such as
continuous level of detail for large model display, as well as the bug fixes
mentioned above and more.

4) The SGI version is IRIX only! It probably can be ported to Linux readily.
And it has been ported to Windows by others (TGS of course, plus Portable
Graphics before they were absorbed by TGS, and at least one other company),
but the Windows ports are not open source.

5) Open Inventor is not really designed to deal with large immersive worlds.
Its fine for inspecting CAD models and collections of objects.

If you're a Linux developer, you might consider using IRIS Performer (to be
OpenGL Performer with next version), which is freely available for Linux
(binaries only). It is better suited for large models and environments, and
it is designed to actively manage performance/frame rate. Probably a better
choice for games, but there is no Windows version and likely never will be.
See this link:

http://www.sgi.com/software/performer/

Graham Rhodes

> -----Original Message-----
> From: gda...@li...
> [mailto:gda...@li...]On Behalf Of Ko,
> Manchor
> Sent: Tuesday, September 05, 2000 12:38 PM
> To: gda...@li...
> Subject: RE: [Algorithms] FW: [CsMain] Scene Graphs
>
>
> Yes - and of coz read the classic Performer paper. I believe it
> is Siggraph
> 96 by Ruelfe and Hellman.
>
> -----Original Message-----
> From: Graham S. Rhodes [mailto:gr...@se...]
> Sent: Tuesday, September 05, 2000 7:14 AM
> To: gda...@li...
> Subject: RE: [Algorithms] FW: [CsMain] Scene Graphs
>
>
> At SIGGRAPH 1999 there was a paper/panel session called "Scene
> Graphs: Wired
> or Tired" to discuss this, although not necessarily from a game
> development
> standpoint.
>
> Here are a couple of links that should give you part of the
> content of that
> presentation (if you don't have the SIGGRAPH proceedings already):
>
> http://www.intrinsic.com/technology/presentations.htm
> http://www.cs.brown.edu/research/graphics/research/siggraph99/scenegraph/
>
> Graham Rhodes
>
> > -----Original Message-----
> > From: gda...@li...
> > [mailto:gda...@li...]On Behalf Of Aaron
> > Drew
> > Sent: Saturday, September 02, 2000 7:56 PM
> > To: gda...@li...
> > Subject: [Algorithms] FW: [CsMain] Scene Graphs
> >
> >
> > I've read many discussions on this list as to the pro's and con's
> > of various
> > solutions to storing, rendering and processing 3D objects but the
> > scene-graph hasn't really made much discussion since I've been
> subscribed.
> >
> > I can't seem to find much on the web in regards to their
> usefulness apart
> > from a few papers on VRML and Java3D.
> >
> > I'm having trouble seeing how the added cost of unnecessary traversal of
> > nodes and the memory overheads of parent/child links in a scene would be
> > worth the added effort but I'm curious as to the thoughts of the many
> > experienced developers on this list.
> >
> > Do scene-graphs pay off?
> >
> > If so, how?
> >
> > Managing vertex buffers, textures, multiple instances of objects (with
> > shared vertex data), etc can get rather clumsy without a
> consistant system
> > yet everything I've read about scene-graphs suggests that they
> are simply
> > traversed and the objects in them rendered. How would I
> represent (say) an
> > octree implementation within a construct like
> > this?
> >
> > - Aaron
> >
> > _______________________________________________
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> > GDA...@li...
> > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
> >
>
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