[osg-users] Dynamical loading of resources

[Robert Osfield]

Hi Joachim,

On 15 August 2017 at 14:21, Joachim Gehrung <
joachim.gehrung at iosb.fraunhofer.de> wrote:

> ok, thank you. I think I'm starting to get the picture :). When you talk
> about a database, you mean just a bunch of files on the filesystem, not
> some kind of SQL database, right?
>

It could be either...

For VPB generated paged database what you have is set of files, with one
file as the topmost and lowest level of detail that your application loads
and then this topmost file contains a PageLOD that references a file
contains the next level details and so on.  With a quad tree you get four
more files for each level, for an octree you get eight more files.

For osgEarth it dynamically creates the PagedLOD subgraphs in that extract
image and elevation data from online or local raw data sources.

Other users have written custom osgPlugins that use tile references encoded
into the PagedLOD filename strings that the custom plugin uses to read from
an external source. some have even done this extracting the data from a SQL
database.


> I'm afraid I have to implement against our own backend. So let my guess, I
> would have to implement a subclass of the osgDB::DatabasePager to handle
> that?
>
>
Um... how many times do I have to say you don't need to subclass from
DatabasePager.

Repeat after me:
    I don't need to subclass from DatabasePager.
    I don't need to subclass from DatabasePager.
    I don't need to subclass from DatabasePager.

:-)

All you need to do create a paged database using standard
osg::PagedLOD/osg::Geometry Nodes, you can do this offline like VPB or on
the fly like osgEarth.  I suspect a custom plugin might be the way from for
yourself, but this is just a guess, you haven't said anything how you data
is stored and should be accessed.  Please share info on how your data
stored and what it represents, this will help guide you in the right
direction.

Robert.
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