[osg-users] Memory leak when using a pixel buffer to generate thumbnails

OpenSceneGraph Users osg-users at lists.openscenegraph.org
Wed Jun 24 00:14:42 PDT 2020

Thanks Robert, excellent answer.

I think I have enough for a way forward now.
One small remaining question,

Does readRefNodeFile access GL at all for any of these file 
Or, to put it another way, can readRefNodeFile be called safely from a 
std:async thread to return something containing a usable osg::Node within 
the main application?



On Tuesday, 23 June 2020 18:10:21 UTC+1, Robert Osfield wrote:
> I can;t say what the leak will be from the code supply but I can say that 
> creating a dedicated viewer, rendering a frame, then destroying really 
> isn't an efficient way to go about generating a thumbnail image.  Rather 
> than than debug a dubious approach I'd suggest you leave it and try another 
> lighter weight approach.
> The best approach is something I can't say at this point as I don't know 
> enough about your application and your needs for generating a thumbnail.  
> Is it a one off activity, something you do offline, something that is done 
> occasionally?  How to go about things depends upon your usage case.
> As a general comment, creating an destroying objects on OpenGL and 
> consequently the OSG is expensive.  It's far better to create once and 
> reuse, even if you don't reuse often.
> Also creating separate graphics context is very expensive, if you already 
> have a graphics context then the best thing to do for offscreen rendering 
> is to your a frame buffer object and render to texture.  This way you can 
> minimize the amount of new GL objects being created for the task,  W.r.t 
> running in a background thread, OpenGL isn't a multi-threaded API, you can 
> only multi-thread with multiple graphics context with t a thread per 
> context.  It's only really suitable for mulitple GPU tasks.  It's typically 
> far better to just add the work to the standard frame and run it as part of 
> your normal viewer.
> With the OSG you can toggle on/off render to texture by setting the 
> NodeMask of an osg::Camera.

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