Paged LOD are LOD where SubLevels are stored into the main memory only when
needed (paged), the level of details that are not used are removed from the
memory to free place.
A Normal LOD has all its levels into memory, even if not drawed. A Paged
does not.

Behind that, there is an intellegent system to store/unstore fairly the
sublevels.

2007/2/15, Robert Osfield <[EMAIL PROTECTED]>:

On 2/15/07, RJ <[EMAIL PROTECTED]> wrote:
> Hi Guys,
> Can any one tell me, what is the difference between LOD and pagedLOD ?
> thanx in advance

PagedLOD is just an an LOD and is even subclassed from LOD, what it
adds extra is a filename field per child, where the filename can be
used to reference a file (even one on the net) or encode a tile
reference for psuedo loaders to generate geometry/textures
automatically.

When the cull traversal hits a PageLOD and finds a child that it need
isn't loaded yet it'll make a request to load it in a via the
osgDB::DatabaseBase which runs a background thread to do the loading,
and rather than wait for the tile to load it fallbacks on the next
highest level of detail child that is available.  The viewer keeps
checking for tiles that have been loaded and automatically loads them
in when ready.

There is also an automatic system for expiring subgraphs that are no
longer in view, so these subgraphs are deleted and their OpenGL placed
on buffer ready to be re-used when possible.

The viewer/DatabasePager work to ensure that the system is loaded
balanced to help achieve database paging without frame drops.

Robert.
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