Hi Robert,
I can submit a fix then.
Thanks for the quick reply.
Cheers,
Anish
robertosfield wrote:
> Hi Anish,
>
>
>
> I think you are correct, the way to handle concurrrent reading/updates of an
> osg::Image is to take a local copy of the osg::Image::getModifedCount() prior
> to reading from the image and then use this value. This would still have the
> danger of the image data being updated at the same time as it's being read
> but at least a texture update wouldn't be missed.
>
>
> Robert.
>
>
>
> On 17 October 2017 at 09:38, Anish Thomas < ()> wrote:
>
> > Hi,
> >
> > While modifying texture-atlases in DBPager threads we noticed an issue of
> > thread-synchronization.
> >
> > Code like the snippet below (From Texture2D.cpp):
> >
> > else if (_image.valid() && getModifiedCount(contextID) !=
> > _image->getModifiedCount())
> > {
> > applyTexImage2D_subload(state,GL_TEXTURE_2D,_image.get(),
> > _textureWidth, _textureHeight,
> > _internalFormat, _numMipmapLevels);
> >
> > // update the modified tag to show that it is up to date.
> > getModifiedCount(contextID) = _image->getModifiedCount();
> >
> > }
> >
> > If another thread (like a DBPager thread) modifies the image of a texture
> > (in this case a texture-atlas which gets more and more images added to it
> > while it is also being applied on geometry), the modified count changes
> > made by one or more dirty() calls can get missed.
> >
> > If the image got dirtied before the RenderThread tried to apply this
> > texture, code-execution enters the if() described above. If the texture
> > upload takes too long and the image is dirtied again, the effect of the 2nd
> > dirty can be missed when the modified count of the image is put into the
> > texture.
> >
> > A simple solution would be to use a local variable to store the image's
> > modified-count, and apply it to the texture. The overhead of a possible
> > redundant texture-upload on the next apply would be down-side. But
> > texture-atlases would support multi-threaded updates better.
> >
> > Thoughts?
> >
> > Thank you!
> >
> > Cheers,
> > Anish
> >
> > ------------------
> > Read this topic online here:
> > http://forum.openscenegraph.org/viewtopic.php?p=72188#72188
> > (http://forum.openscenegraph.org/viewtopic.php?p=72188#72188)
> >
> >
> >
> >
> >
> > _______________________________________________
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> > ()
> > http://lists.openscenegraph.org/listinfo.cgi/osg-submissions-openscenegraph.org
> >
> > (http://lists.openscenegraph.org/listinfo.cgi/osg-submissions-openscenegraph.org)
> >
>
>
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Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=72191#72191
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