[osg-users] PagedLOD and page in/out detection

[Robert Osfield]

Hi Nick,

It's *really* inefficient to use an update callback to do this type of
task, I can not recommend going this path, it's waste of both our time
trying to coax it to do something useful.

The right way of doing it is by overriding the
DatabasePager::updateSceneGraph() method or implementing you own
equivalent method in the Viewer::updateTraversak() in place of current
calls to updateceneSceneGraph().

Robert.

On 3 June 2016 at 18:28, Trajce Nikolov NICK
<trajce.nikolov.nick at gmail.com> wrote:
> Hi Robert,
>
> this is my update callback .. And I know for sure it was working. I just did
> a clean app (modified osgviewer with only this callback installed in the
> root PagedLODs) and I never see a Paged Out tile ... I am limited to not
> having the possibility to make a custom DatabasePager or it will go really
> complicated. The root PagedLOD can have only one or zero children (that is
> the test database I am testing it against)
>
> struct UpdateCallback : public osg::NodeCallback
> {
> UpdateCallback()
> : _numChildren(0)
> {
>
> }
> virtual void operator()(osg::Node* node, osg::NodeVisitor* nv)
> {
> osg::PagedLOD* plod = dynamic_cast<osg::PagedLOD*>(node);
> if (plod)
> {
> if (plod->getNumChildren() != _numChildren)
> {
> _numChildren = plod->getNumChildren();
>
> if (_numChildren)
> std::cout << "Paged in" << std::endl;
> else
> std::cout << "Paged out" << std::endl;
>
> }
> }
> traverse(node, nv);
> }
> protected:
> int _numChildren;
> };
>
> On Fri, Jun 3, 2016 at 6:49 PM, Robert Osfield <robert.osfield at gmail.com>
> wrote:
>>
>> Hi Nick,
>>
>> There isn't a feature directly built into osg::PageLOD or
>> DatabasePager for this.
>>
>> What you could do is look at the  creating a custom DatabasePager that
>> overrides the following method:
>>
>>        /** Merge the changes to the scene graph by calling calling
>> removeExpiredSubgraphs then addLoadedDataToSceneGraph.
>>           * Note, must only be called from single thread update phase. */
>>         virtual void updateSceneGraph(const osg::FrameStamp& frameStamp);
>>
>> Within this you could add your own tracking of when things are merge or
>> removed.
>>
>> Robert.
>>
>>
>>
>> On 3 June 2016 at 17:15, Trajce Nikolov NICK
>> <trajce.nikolov.nick at gmail.com> wrote:
>> > Hi Community,
>> >
>> > I was looking for a way to detect when PagedLOD gets its children paged
>> > in/out. So I installed an update callback and based on a difference in
>> > the
>> > children number I was able to know when such change occurred. And this
>> > was
>> > working with a code an year ago.
>> >
>> > Now it doesn't .. Any clue or hint how to detect such changes?
>> >
>> > Thanks a bunch as always!
>> >
>> > Cheers,
>> > Nick
>> >
>> > --
>> > trajce nikolov nick
>> >
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>> >
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>> >
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>
>
>
>
> --
> trajce nikolov nick
>
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