Robert Osfield wrote:
HI Bret,

On Thu, Jun 4, 2009 at 6:18 PM, brettwiesner<> wrote:

Just validating some assumptions about the database pager...
1) Is paging in single threaded mode blocking? If OSG is in single threaded
mode, will the pager load data and stop rendering or will it load in another
thread anyway?

As others have said the DatabasePager it totally orthogonal to the
osgViewer::Viewer/CompositeViewer, so the pagers threading works
regardless of what you do with the viewer.

2) If OSG is running in multithreaded mode will the pager load data

The DatabasePager always loaded asynchronously - that's the whole point of it.

Now some real questions:
3) How does the pager decide when to page something in?

When PagedLOD nodes that are encountered during the cull traversal
require an external tile that isn't loaded yet they makes a request to
the loaded the tile.

4) How does the pager decide when to page something out?

That depends upon the mode the DatabasePager is set up with.  The
current default in 2.8.0 onwards is to mainatain a maximum number of
active PagedLOD and to prune inactive branches when that number is
exceeded.  Note, it only prunes inactive branches, it never touches
the active ones i.e. the ones on screen,

5) How does the pager page something out?

It maintains a list of expired subgraphs and during the update
traversal these subgraphs are removed.

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