[osg-users] Multiple viewers and one scene
nicolas peña
As I need to control the frame rate of my cameras independently, I have set-up a viewer for each one.
One camera has to draw in a window and accept user input, while the others should not appear in the screen at all
(they have an image attached and send a copy of it to other process).
To achieve this, the interactive camera's graphic context is set from a traits with pbuffer = false
and the other one with pbuffer = true.
The problem is that if a set up a loop that calls the frame method of both one renders over the other as
if the rendering contexts were the same.
Can I share the scene among different viewers?
If yes what do I need to do to render properly?
Please ask for the needed details...
Thanks a lot,
Nicolas.
Robert Osfield
Its really hard to know whats going on at your end w.r.t application
setup and flow control so advicing on it is easy. In general I can
say that sharing a scene between View's is OK within on
CompositeViewer as they will Views on the same scene will share the
same FrameStamp i.e. there will be all at the same point in time.
Sharing one scene between multiple Viewers will hit up against the
problem that in one set of traversals the scene graph is one time and
then the traversals from the other viewer will try to change the time
back - and likely to cause a mess. This timing issue isn't likely to
cause problems with high level rendering though - it should just mess
up things like particle systems and sequences.
Robert.
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nicolas peña
I have done several tests and have reached to the conclusion that it is not possible
to use two viewers at the same time from one process.
This happens even when they do not share anything and even if I set-up
the viewers from different threads.
I have done the most simplistic code and even this fail.
I'm using OSG 2.3.4 on Linux 2.6.22 with NVIDIA proprietary drivers.
I would like to help to solve this if you confirm it as a bug and if it is possible.
Thanks a lot,
Nicolas.
nicolas peña
Thanks again,
Nicolas.
Robert Osfield
On Fri, Feb 22, 2008 at 7:11 PM, nicolas peña <mr.an...@gmail.com> wrote:
> I have done several tests and have reached to the conclusion that it is not
> possible to use two viewers at the same time from one process.
Are you running the viewers single threaded? If so then the lazy
setting of makeCurrent for each for the viewers will mean that after
the first frame the makeCurrent won't be called as the viewer assumes
that it already has the context current so can save the cost of the
makeCurrent. Interleaving two viewers in the same thread would then
cause one viewer's GraphicsWindow to be the one that is current and
the other will never be updated. osgViewer hasn't been designed for
this usage model - one that I haven't ever thought of as a combination
in fact - its support may different combinations of viewer usage but
just not this one I'm afraid.
Potentially we could modify osgViewer::ViewerBase to allow you to use
the viewer in this way i.e. have two viewers called from the same
frame loop thread, this would require switching off the lazy
makeCurrent mechanism - the method that does it is
ViewerBase::makeCurrent(osg::GraphicsContext* gc) that you'll find in
include/osgViewer/ViewerBase. Perhaps a bool flag in ViewerBase could
be used to enable the lazy makeCurrent() for instance.
> This happens even when they do not share anything and even if I set-up
> the viewers from different threads.
> I have done the most simplistic code and even this fail.
> I'm using OSG 2.3.4 on Linux 2.6.22 with NVIDIA proprietary drivers.
>
> I would like to help to solve this if you confirm it as a bug and if it is
> possible.
You usage model is rather unusually so you using osgViewer out of
scope, so rather than bugs its most design limitations. The OSG is
not a static object - it evolves over time in response to being pushed
into new spheres and usage models, this sometimes requires big
refactoring to open the news ways of using it, but often a little
tweak here or there can deliver a lot.
I haven't fully got my head around your usage model, so I'd suggest
writing an example that could go in OpenSceneGraph/examples that
illustrates what you are trying to do, but its failing. This example
could then be used by others to see the problem first hand and then a
solution could be found, but it a tweak to the example or a tweak to
osgViewer itself.
Robert.
nicolas peña
I will write the example for better understanding of what I am trying to do and look at the code you suggested.
I'll derive it from the code in osgwindows (setting one camera for each window in an independent viewer) and
post it here as soon as possible.
Just in case you are curious about my case of use, I will try to explain a bit my intentions, if you consider that my
approximation is not right please correct me.
I am building a simulation framework aimed at multi-robot collaborative perception. I am going to implement this
using a composite viewer with at least two views for the simulator user interface, plus a dynamic number of viewers,
one for each simulated camera as I need to be able to set the frame rate of the cameras independently.
The cameras of these viewers would render to a pbuffer each and have an image attached in order to send then to the
artificial vision algorithms. I also need to share the scene across all the viewers.
Thanks,
Nicolas
.
Robert Osfield
> Just in case you are curious about my case of use, I will try to explain a
> bit my intentions, if you consider that my
> approximation is not right please correct me.
> I am building a simulation framework aimed at multi-robot collaborative
> perception. I am going to implement this
> using a composite viewer with at least two views for the simulator user
> interface, plus a dynamic number of viewers,
> one for each simulated camera as I need to be able to set the frame rate of
> the cameras independently.
> The cameras of these viewers would render to a pbuffer each and have an
> image attached in order to send then to the
> artificial vision algorithms. I also need to share the scene across all the
> viewers.
My guess is that this should probably be possible given separate
threads for each of the viewers frame loops i.e. run them all in a
background thread. Sharing of images is possible by using a frame
buffer copy to osg::Image, or just having multiple FBO's all within
one graphics context. If you can have the frames all done
synchronously then perhaps you could have one frame loop and just
disable the cameras that you don't need updating on each frame, i.e.
main viewer runs at 60Hz, and the other RTT cameras run at 20Hrz so
get update on frame in 3.
nicolas peña
>synchronously then perhaps you could have one frame loop and just
>disable the cameras that you don't need updating on each frame, i.e.
>main viewer runs at 60Hz, and the other RTT cameras run at 20Hrz so
>get update on frame in 3.
Sorry for my lack of knowledge but, can you tell me how can I deactivate/activate
the cameras ?.
I don't find the proper method.
Thanks a lot,
Nicolas.
Robert Osfield
> Yes, I think I'll be OK with that.
> Sorry for my lack of knowledge but, can you tell me how can I
> deactivate/activate
> the cameras ?.
> I don't find the proper method.
camera->setNodeMask(0x0);