Jie,

Robert gave you a lot of good info, but I just wanted to add a few things:

VR Juggler (http://www.vrjuggler.org) comes with an OSG-based application example if you are just looking to load & navigate OSG-compatible models on a cluster.

I'd advise against using Chromium based on the bandwidth requirements which translate into poor performance. However, if you go with Chromium on an X-Windows system, you might want to try DMX with a Chromium back-end to turn your tiled wall into one large desktop.

-Todd

On 5/16/2009 2:47 AM, Jie Liu wrote:
Hi,

thank you all, people. Your information are very important.

I believe we have to re-evaluate our plan.
I'd like to search for more information about multi-display wall stuff.

Wish you all a good day~ :-)


2009/5/15 Robert Osfield <[email protected]
<mailto:[email protected]>>

    Hi Joe? Jie, could you please sign with your first name so I know
    which one to use when addressing you rather than having to do a best
    guess, thanks,

    On Fri, May 15, 2009 at 10:41 AM, Joe L <[email protected]
    <mailto:[email protected]>> wrote:
     > In our plan, the TDW will have around 30 displays.

    OK, you'll definitely need a cluster for this.

     > Do you mean that :
     > If I would like to use OSG, I will have to additionally do the task
     > management, network synchronization, and distributed rendering?

    The OSG doesn't provide this cluster manage functionality, it's
    focused on rendering on a single image system, albeit with
    capabilities of doing multi-thread, multi-screen output.

    The two options you have right now are to go with a distributed GL
    implementation such as Chromium, or a distribution application
    implementation such as facilitated by libs like Equalizer.

    There is a third possible solution would require mods to the core OSG,
    or at least subclasses from it, and is something I've been wondering
    about for a while.  The approach would be to do a distributed render
    graph, where you do a cull traversal (or several cull traversal) on
    the master for the whole view frustum that gives you a list of
    drawables, modelview+projection matrices and state inheritance graph,
    then you broad cast this list to slaves on the cluster.  These then
    traverse this rendering graph and cull out what leaves aren't in their
    local view frustum.  On each slave you'd cache the state and geometry
    and update this only when the master changes their value, to avoid
    having to dispatch all this data on each new frame.

    The distributed render graph proposal above sits between the low level
    distributed GL approach and the high level distributed application
    approach like done with Equalizer.  The distributed GL approach
    requires more network and CPU bandwidth, most doesn't require any
    application modifications to do the cluster, while the distributed
    application approach minimizes network bandwidth but does require you
    to design your application with the cluster in mind.  The later
    approach is more work, but provides better scalability.

    The distributed render graph approach has the potentially of scaling
    reasonable well, while at the same time need little more than a
    cluster specific cluster configuration being used in the viewer, so
    once you have this inbuilt capability it's would be easy to move from
    a single desktop display to a cluster by just changing a viewer
    configuration file.

    Robert.
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--
Jie Liu
Visualization Research Group
Center for Information Science, School of EECS,
Room 2104, Science Building No.2,
Peking University, Beijing 100871, China


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