On Wed, Sep 11, 2013 at 9:31 AM, Robert Osfield
<[email protected]> wrote:
> What stands out is that you are doing stuff that is probably not the best
> way to do it. To find out the best way it would be better to explain what
> you are tying to do with your application w.r.t views, graphics contexts,
> threads, scenes and then let us suggest what to do.
Fair enough. Thank you for your patience and assistance. My
application is quite simple.
I have a scene that contains a terrain, imagery overlayed atop the
terrain, and some objects wandering around on the terrain. I create
this scene using osgEarth (osgEarth::Map, osgEarth::MapNode, etc).
I'll call this the "Load" operation.
Initially I have zero viewers. However, from time to time I am
notified (via a network connection) that someone wants to view the
scene. When this happens I create a Viewer and attach the scene data.
I use a pbuffer and associated callbacks to produce a JPG of the
scene and send the video back via the network connection. I'll call
this the "NewViewer" operation.
Via the network the I am told where this viewer is and which way he is
looking. I forward this information to the camera via a very simple
manipulator that is attached to my view. I'll call this the
"MoveCamera" operation.
Via the network I am told that a viewer is no longer interested in
existing. I remove the viewer. I'll call this the "DeleteViewer"
operation.
Pseudocode:
main()
{
osg::ref_ptr<osg::Node> pNode = Load();
osg::ref_ptr<osgViewer::CompositeViewer> pCompositeViewer = new ...;
vector<osg_ref_ptr<osgViewer::Viewer> > Viewers;
while (true)
{
while (PendingNewViewer)
{
Viewers.push_back(NewViewer(pCompositeViewer));
}
while (PendingDeleteViewer)
{
DeleteViewer(pCompositeViewer, Viewers);
}
for (auto pViewer : Viewers)
{
MoveCamera(pViewer);
}
if (!Viewers.empty())
{
pCompositeViewer->frame();
}
}
}
===
Questions:
Q0: Is this a reasonable use of OSG?
Q1: Should I use a composite viewer (as shown in the pseudocode) or
just "many viewers each attached to the same pNode"?
Q2: Should this work when there are zero viewers at startup?
Q3: Should this work as the number of viewers changes, e.g. from 0->2->0->4
A3: No. Not when you use a composite viewer. The scene turns
"purple" with this pseudocode.
Thank you,
Chris
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