[osg-users] osgText 3.6.3 crash

Robert Osfield robert.osfield at gmail.com
Wed Sep 12 07:09:02 PDT 2018

Hi Nick,

There are plenty of ways mutlti-thread setting of Text labels could
cause problems if the threads reading from the Text are running in
parallel to the ones setting it.  A mutex "might" help but it could
easily be done in the wrong way.  If you are modifying text
dynamically then you should set the DataVariance to DYNAMIC.  However,
adding mutex and using DataVariance of DYNAMIC might protect things if
you do it all right but performance issues can easily become dominant
as it can easily stall the various threads.

It may be that trying to dynamically update Text is simply the wrong
solution for your application.  It might be that writing your own
custom shader to implement text is the better thing to do.


On Wed, 12 Sep 2018 at 13:24, Trajce Nikolov NICK
<trajce.nikolov.nick at gmail.com> wrote:
> Hi Robert,
> we are experiencing some crashes in our sim software. And I know you will not like this post since I can not produce minimal case exercising this issue - I tried to mimic the sim code into one simple app but in this minimal app all works just great. So I will try to explain and count on you with hints
> The environment is multithreaded:
> - high res thread updating labels guarded by mutex
> - the osg threads with update callbacks on osgText::Text that is setting the labels with setText(...) guarded  by mutex
> The env is XUbuntu 18, NVIDIA GTX 1080
> And the crash happens at
> Text::drawImplementationSinglePass ln: 1151 glyphquad._primitives->draw(state, usingVertexBufferObjects);
> which furthers
> DrawElementsUShort::draw ln: 266
> if (_numInstances>=1) state.glDrawElementsInstanced(mode, size(), GL_UNSIGNED_SHORT, (const GLvoid *)(ebo->getOffset(getBufferIndex())), _numInstances);
>             else glDrawElements(mode, size(), GL_UNSIGNED_SHORT, (const GLvoid *)(ebo->getOffset(getBufferIndex())));
> _numInstances is 0 when the crash happens so the crash happens here:
> glDrawElements(mode, size(), GL_UNSIGNED_SHORT, (const GLvoid *)(ebo->getOffset(getBufferIndex())));
> Any clue or at least a thought when this can happen? Mean while I will continue testing and will really try again to make a small app reproducing this behavior
> Thanks a bunch as always!
> Cheers,
> Nick
> --
> trajce nikolov nick
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