[osg-users] Function collaboration multi-threaded databasepager

Robert Osfield robert.osfield at gmail.com
Wed Sep 5 03:27:29 PDT 2007


Hi Lambert,

I'm afraid I don't have time to walk you though all the code, only
time to point people in the right direction.

There has been a lot discussed about database paging on the list over
the years so have do searchings on the archives.  Perhaps others on
the lists can help you along the learning curve too.

Robert.

On 9/5/07, Lambert Verhagen <l.verhagen at marin.nl> wrote:
> Hi Robert,
>
> Thanks again for your reply.
>
> I have been browsing the databasepager code and how it interacts with a
> plugin. Do I understand it correctly if I say: ?????
>
> The scenegraph on the simulation loop is pulling the data via the
> database pager from a plugin. The scenegraph request the database pager
> for new data (graph nodes).
>
> But what if I want the plugin to push the data to the simulation loop?
> How do I do that? Does the databasepager support that?
>
> Regards,
> Lambert.
>
>
> On Mon, 2007-09-03 at 13:46 +0100, Robert Osfield wrote:
> > Hi Lambert,
> >
> > The existing DatabasePager functionality can page over the network,
> > but this isn't an issue for the DatabasePager - its purely a function
> > of the net plugin that does the loading across the http.  This means
> > paging and reading across the network are completely orthogonal and
> > can be mixed and matched at will.
> >
> > The Viewers already have support for adding and remove subgraphs from
> > the main scene graph via the DatabasePager.  You needn't add your own
> > code as long as the database is set in a way that utilises
> > DatabasePager.
> >
> > You can write your own DatabasePager functionality, but it its likely
> > to be alot less work just to use the built in paging support, this way
> > the task for you is just how to build you database.  Teaching you how
> > to reimplement existing functionality really is way beyond the level
> > of support I can provide for free.
> >
> > Robert.
> >
> > On 9/3/07, Lambert Verhagen <l.verhagen at marin.nl> wrote:
> > > Hi Robert,
> > >
> > > Thank you for the quick response.
> > >
> > > I don't understand it completely. Must be me not questioning right ;-).
> > >
> > > What I want to develop is an application that:
> > > 1) reads data that may contain from scene data like new nodes that are
> > > moving (AddNode). This data feed may also result in a removeNode (since
> > > another application may have decided to remove it from the scene. The
> > > scene graph is constantly, dynamically changed.
> > > 2) has an Update-Cull-draw pipe, that runs synchronous (real-time) and
> > > in the update step reads data from the graph that is dynamically changed
> > > by step 1.
> > >
> > > For this I thought I need an a-synchronous database thread that read
> > > data from the network (other application) and fills the database at
> > > low(er) frequency. And I also need a fast synchronous thread that reads
> > > data from the database (this must be quick, so probably I need
> > > references to the database scene graph nodes).
> > >
> > > The applications like Viewer en CompositeViewer perform updates to the
> > > scene graph via NodeCallbacks that are called from the same thread as
> > > the update-cull-draw thread is running. Isn't it????
> > >
> > > Hope you can me further.
> > >
> > > Regards,
> > > Lambert
> > >
> > > On Mon, 2007-09-03 at 09:52 +0100, Robert Osfield wrote:
> > > > Hi Lambert,
> > > >
> > > > The OSG has the osgDB::DatabasePager which sole purpose is to do
> > > > multi-threaded paging of databases.  The osgViewer::Viewer and
> > > > CompositeViewer both support it out of the box, as did
> > > > osgProducer::Viewer before it.  There is nothing you need to do in
> > > > your app other than load a paged database. Paged dabases in the OSG
> > > > are ones that contain osg::PagedLOD node or loaded via the TXP plugin.
> > > >
> > > > Robert.
> > > >
> > > > On 9/3/07, Lambert Verhagen <l.verhagen at marin.nl> wrote:
> > > > > Hi,
> > > > >
> > > > > I investigating the usage of openscenegraph for one of our application.
> > > > > I want to run this application using 1 thread for the update-cull-draw
> > > > > pipe. And another thread, that runs on the background with lower
> > > > > priority, that receives data from some external network and updates the
> > > > > graph.
> > > > >
> > > > > I can not exactly find a sample application using this multi threaded
> > > > > approach. But the function interface of databasepager suggests that this
> > > > > is supported. Can someone give me a clue?
> > > > > I also want to know the function collaboration between the view,
> > > > > updateVisitor, node and dataBasePager classes.
> > > > >
> > > > > Hope you can help me?
> > > > > Thanks in advance.
> > > > > Regards,
> > > > > Lambert
> > > > >
> > > > >
> > > > > Interested in MARIN's R&D 2007? Subscribe to the MARIN R&D seminar for the Dutch Industry on September 12.
> > > > >
> > > > >
> > > > > This e-mail and its content are subject to the disclaimer and General Conditions at www.marin.nl
> > > > >
> > >
> > >
> > > Interested in MARIN's R&D 2007? Subscribe to the MARIN R&D seminar for the Dutch Industry on September 12.
> > >
> > >
> > >
>
>
> Interested in MARIN's R&D 2007? Subscribe to the MARIN R&D seminar for the Dutch Industry on September 12.
>
>
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