[osg-users] How do PagedLOD children expire?

Paul Martz pmartz at skew-matrix.com
Mon Sep 10 14:30:40 PDT 2007


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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