Osland, CD (Chris) C.D.Osland at rl.ac.uk
Fri Aug 30 08:30:26 CDT 2002

On the protocols front, I obviously need to do some homework!

On the 3D side of things, we've been observing (rather than looking
into!) this for about 7 years, since the time we set up a VR Centre.
About the only firm conclusion is that ... it depends!  Some 3D
models are small, some are large; some are constant content but
variable geometry (e.g. a mannequin) while others are variable
geometry (e.g. an isosurface mesh as the surface value is changed);
some are stored in a way that is appropriate, others are not; some
model changes are actually just camera changes for a constant model,
others really are changes to the model; some images of 3D objects
are small, some are large, some are stereo or tiled (e.g. caves)!

In short, some changes to images of 3D models can be described by an
amount of 'structural' data less than the data required to convey a
changed image, and for others the reverse is true.

We recently did some work over the AG between here (RAL in the UK)
and CalTech with VNC distributing Iris Explorer sessions running
at both sites, and using the data sharing tools in Iris Explorer
We found that having both VNC and video feeds of both ends at both
ends was a great help - e.g. someone in CalTech could use the shared
mouse to alter parameters on the RAL application and see the result
immediately over the video link (albeit a bit fuzzy), and would
subsequently get the loss-less version via VNC.  Sharing the actual
data via COVISA was great for small models and really slow for
large models (not helped by the CalTech model running on a laptop
that was connected by Wi-Fi - not really 100 Mbps)!!!  I'll see
whether the report the people running the test produced is on the
web yet, and if so make the URL known.



Chris Osland                         Office tel: +44 (0) 1235 446565
Digital Media and Access Grid      Medialab tel: +44 (0) 1235 446459
BIT Department             Access Grid room tel: +44 (0) 1235 445666
e-mail:   C.D.Osland at rl.ac.uk               Fax: +44 (0) 1235 445597

CLRC Rutherford Appleton Laboratory (Bldg. R18)
Chilton, DIDCOT, Oxon OX11 0QX, UK

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-----Original Message-----
From: Luc Renambot [mailto:renambot at cs.vu.nl]
Sent: 30 August 2002 13:31
To: ag-tech at mcs.anl.gov
Subject: RE: [AG-TECH] HDAG

Interesting topic ! I'd would be interested in some discussion.

Few thoughts:
  - few people seems to use RTPtv (over internet2 I think)
     Hardware + Software solution, integrated in OM vic,
     for full D1 over IP.
  - More and more video players start support some form 
    of RTP (Mplayer, VLC from videolan). They also use
    "modern" codecs (divx, mpeg4,...), and are open-source.
  - How to do 3D graphics: 3D api or pixels/video streaming
  - ...


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