Hi Terry,

I haven't been following this thread very closely, but is your essential
problem that things look correct until the pager needs to load
something, resulting in a hole until the data is finally loaded?

You can get around this by having adding the lowest level of detail
loaded directly into the scene graph as the first child in your PagedLOD
using addChild.  It will stay there at all times, and ensure that
*something* is always displayed, even when paging.  I've used a similar
approach on my project and it works really well.

Thanks,

Jason

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Terry Welsh
Sent: Tuesday, January 09, 2007 12:55 P
To: [email protected]
Subject: Re: [osg-users] PageLOD holes

>
> Hi Terry,
>
> On 1/8/07, Terry Welsh <[EMAIL PROTECTED]> wrote:
> > Hi Chris,
> > These PagedLOD holes were the main reason I have given up on writing
a
> > simple Metaflight loader (I emailed the list about that this
morning).
> >  You're right; subclassing PagedLOD was very difficult.  I was
trying
> > to use a NodeVisitor to seek out PagedLODs with unloaded data, and
> > it's just too much of a headache.
> >
> > For now it looks like I'll have to give up on a simple MetaFlight
> > loader and complicate the code by adding my own paging utility
(maybe
> > based on NodeVisitor::DatabaseRequestHandler, or maybe not.  I
haven't
> > decided yet).  If you have any other thoughts on the subject I'd be
> > glad to hear them.
>
> It's sad to hear you giving up.  Unfortunately I'm swamped with work,
> and don't have any knowledge about the specific requirements of
> MetaFlight to be able to help.

MetaFlight is pretty simple geometrically (much simpler than txp from
what I understand).  My fundamental problem is that LOD and PagedLOD
want to switch which children are traversed as soon as the eye
distance changes.  I need to delay these switches until the proper
geometry is loaded, and there is no functionality built into OSG for
doing this.
>
> It certainly is possible to get things loading without holes with the
> appropriate contruction of the scene graph - this is just what osgdem
> does.  The txp plugin also work just fine, but txp adds a number of
> extra steps on top of standard paging to ensure the correct LOD's on
> tile boundaries are selected w.r.t what data is paged in.  Perhaps the
> txp plugin might offer some insight.

I've looked at the txp loader a bit, but it's a very complicated and
undocumented loader.  Unfortunately, I don't have enough time to
figure out all its extra steps and if they apply to my problem at the
moment.
- Terry
>
> Robert.
>
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