On 18 Sep 2013, at 17:05, Stuart Buchanan <stuar...@gmail.com> wrote:
> I did take a look at the PagedLOD approach - Matthias' code made a great
> template to work from.
Yes, that is exactly the model I would follow, and I am sure Mathias can be
asked for additional hints on the best way to integrate it. His SPT system
replaces the tile-scheduling logic with the osgDB Pager, which improve various
things, since osgDB would be fully in control of deciding what is loaded, and
unloaded when, based on the camera(s) - no more arbitrary dealing with rings of
tiles based on visibility parameters.
>
> One thing I wasn't clear on is whether this would move generation of the
> trees/objects/buildings from a scenery loading thread into some other
> thread. I'm not sufficiently familiar with our threading to know if there
> would be any impact.
The ReaderWriters run in the osgDB pager thread, which is exactly where the
current ReaderWriterSTG runs (which ultimately does the current
tree/object/building placement, I think) - so the threading should not change
at all. Indeed, the more I think on it, the more it feels like this should be a
very small restructuring of the code, just requiring some slightly delicate
PagedLOD plumbing to make it work. We're already doing the right work (building
an osg::Node) and doing it in the right thread, we just need to change *when*
we do it.
BTW, I would also hope this means the fixed osg::LOD elements in the quadtrees
could go away, or at least the layering reduced (to one layer of LODs instead
of two) My gut feeling is the LOD-tree is preventing sufficiently large
batching for both trees and random buildings. But of course the optimal batch
size is very hardware dependant.
Regards,
James
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