[osg-users] Trigger some function when PagedLOD finishes openening a node

Bruno Oliveira bruno.manata.oliveira at gmail.com
Mon Sep 12 00:21:30 PDT 2016

Hello Robert,

thank you very much for the detailed answer. I implemented an app based on
Qt. My draw/frame events are only called when the user makes some action
(e.g. Mouse Click, Mouse Move). Is there a way I could bypass this and use
the osgViewer:::ViewerBase::ON_DEMAND option?

2016-09-10 17:36 GMT+01:00 Robert Osfield <robert.osfield at gmail.com>:

> Hi Bruno,
> You could possible use the ReadFileCllback for this purpose.  Have a
> look through the archives for discussions on the different ways that
> ReadFileCallback can be used.
> However, I have to add the the DatabasePager is designed to dispatch
> compile operations to the draw traversal to compile the newly loaded
> subgraphs incrementally during each frame.  A newly loaded subgraph
> isn't merged until all the GL objects in that subgraph have been
> compiled.  This means you can't just switch off doing the rendering
> loop and wait for things to load and just render one frame and expect
> everything to merge right away.  This incremental compilation exists
> to avoid frame drops.
> One way around this pre compilation would be to simply switch off pre
> compilation of subgraphs, this would be new subgraphs are merged in
> the frame right after it has been loaded. However, this approach
> increases the changes of a frame drop as the new data is rendered for
> the first time.
> There is support built into lazy update of the scene via the
> osgViewer::ViewerBase::setRunFrameScheme(...) support for the the
> osgViewer:::ViewerBase::ON_DEMAND option.  When this is set and you
> use the Viewer::run() method the viewer will automatically only call
> frame when events have happened, there are animations running or the
> database requires a new frame to be done (including for the
> incremental compilation.)   You could have a look at how this is
> implemented if you want to do something similar, or just use it
> directly.
> Robert.
> On 10 September 2016 at 09:56, Bruno Oliveira
> <bruno.manata.oliveira at gmail.com> wrote:
> > Hello,
> >
> >
> > I am using a PagedLOD engine, but I need to call some function I have
> every
> > time the PagedLOD finished reading a Node and it is ready for rendering.
> > This function I want to call is intended to trigger a draw/refresh
> action in
> > my viewer, but I think this could be any function at all.
> >
> >
> > How do I do that?
> >
> > Thank you
> >
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