[osg-users] How do PagedLOD children expire?

Zach Deedler zjd at faac.com
Mon Sep 10 15:19:16 PDT 2007


Hello Paul,

 

I went through many pitfalls when I was doing paged databases.  I'll list
them here, and maybe something will catch your eye?

1) Originally I wasn't using osgviewer, and I was loading models on demand.
After you load the model you have to call some function to register the
paged lods.  Osgviewer does this automatically.

2) The paged lod range is different than its culling radius.  Use setRange
for where you want the object to page in/out.

3) Make sure culling is active on the paged lod.

4) There may be some number of objects that are loaded before they start
expiring.

 

  _____  

From: osg-users-bounces at lists.openscenegraph.org
[mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of Paul Martz
Sent: Monday, September 10, 2007 5:31 PM
To: 'Public OpenSceneGraph Users discussion list.'
Subject: [osg-users] How do PagedLOD children expire?

 

Hi Robert -- My understanding of the DatabasePager is that PagedLOD children
that are not visible in the current view volume should eventually "expire",
which I assume means be unloaded from memory. OSG would then have to reload
such children from disk if they ever came back within range. However, I am
not seeing a decrease in process size when PagedLOD children are not
visible. Please let me know if I've somehow misunderstood the intent of the
DatabasePager and PagedLOD.

 

If I understand correctly, the default expiry delay is 10 seconds, so I
should see children being deleted after they are moved outside the view
volume for 10 consecutive seconds.

 

FYI, I'm attempting to cook my own paged database for a tiled OpenFlight
terrain database. I'm doing this with a top-level Group node with several
PagedLOD child nodes, one for each tile in the database. Each PagedLOD has
its own explicit center and radius based on the tile location and size. So,
if you think the issue might be misconfiguration of the PagedLOD nodes, then
I'd say this is possible, though I can't see what I might be doing wrong
from looking at the PagedLOD and LOD headers.

 

I'm using osgViewer, so DatabasePager config is handled automatically.

 

Thanks for any insight,

 

Paul Martz

Skew Matrix Software LLC

http://www.skew-matrix.com <http://www.skew-matrix.com/> 

303 859 9466

 

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