[osg-users] osgQt + OSG 3.6.2 Status

[Wojciech Lewandowski]

Hi, Robert

I find your response as rather harsh and wonder why it hits me. Thats why I
feel the need to reply.

Sigh.... So it's good you guys are getting somewhere.


Sorry, we don't use 3.6 yet and haven't seen this announcement. And I am
glad its fixed in 3.6 already. Its a pity I doubled your effort. But when I
saw my problem and started debugging it I was not aware it will bring me to
our custom QT window creation because at first it looked like osgEarth REX
internal issue. In fact I was not even aware our main window is made as QT
window (pleasures of agile working environment ;-). So when I finally went
through 3 days of debugging I decided to write about my observations
because it sounded like black screen issue mentioned in this thread and was
hoping to save that debugging time for others. Unfortunately I cannot say
it will fixe QT issues others may have, as it was a specific problem with
custom QT integration code loosely based on osgQT from OSG 3.4.x. So my
proposition was also rather loose. I just decided to let people know about
it in hope it may help someone.

 It's not an OSG bug in 3.6.2, it's a bug in your Qt code that was hidden
> from view due to an old bug in the OSG that when fixed revealed the lack
> of proper setup code in custom OSG/Qt integration.


Exactly. This  was a bug in our custom code based on osgQT from 3.4.
Unfortunately I was not involved in making this custom code but had to
integrate new osgEarth REX engine and debuging the issue brought me there.

 If you have custom integration then there isn't anything that osgQt dev's
> or myself can do other than ask you to pay attention when we announce
> fixes and ask you to fix you


Yes, I fixed our custom code by adding setDrawBuffer/setReadBuffer lines.
But I found it and fixed it myself so didn't expect you to do anything
about it. I posted my observations in this thread because wanted to share
the knowledge I gained through long debuging sessions.

Cheers,
Wojtek Lewandowski


pon., 30 lip 2018 o 10:09 Robert Osfield <robert.osfield at gmail.com>
napisał(a):

> Hi Wojtek,
>
> On Mon, 30 Jul 2018 at 08:53, Wojciech Lewandowski
> <w.p.lewandowski at gmail.com> wrote:
> > I understand my setDrawBuffer / setReadBuffer observation was probably
> not the only problem. But I believe this one is genuine problem that should
> not be neglected. So I decide to write this small followup and elaborate a
> bit to make it clearer. In the meantime I did some more research on
> DrawBuffer/ReadBuffer calls made in OSG. [disclaimer]: We use OSG 3.4.0 and
> I did not check latest OSG versions. So if anyone uses later 3.6.x he/she
> may check if my observations are still valid. I did however, noticed that
> plain osgViewer window config setups call camera->setDrawBuffer /
> camera->setReadBuffer for main window cams. See
> osgViewer\config\SingleWindow.cpp for example (search for setDrawBuffer).
> And I did notice that the same is NOT done in osgQT window setup. At least
> in OSG 3.4.0 release we use, osgQT does not call setDrawBuffer /
> serReadBuffer for camera set in QT window.  And I believe this is a bug.
> setDrawBuffer/setReadBuffer should be called for any top window camera.
> Because i
>  f not, and if you add some other camera which will explicitly or
> implicitly invoke glDrawBuffer call with other buffer than the one set by
> default in window creation, you are most likely going to see black screen.
>
> Sigh.... So it's good you guys are getting somewhere.  The sad thing
> is that you are re-inventing the wheel w.r.t the issue.
>
> A few months back I investigated a bug that some osgEarth/Qt users
> were seeing and it was down to missing setRead/setDrawBuffers() a bug
> that had lingered long in the code, bit only recently highlighted
> because of fixes to the core OSG.  I made the fix to osgQt and the
> osgEarth team fixed their Qt example. I made a very clear public
> announcement called for the attention of all Qt users that they should
> add setDrawBuffer/setReadBuffer().  There isn't anything more I could
> have done.
>
> Please go back to my announcement thread.  It's not an OSG bug in
> 3.6.2, it's a bug in your Qt code that was hidden from view due to an
> old bug in the OSG that when fixed revealed the lack of proper setup
> code in custom OSG/Qt integration.  If you have custom integration
> then there isn't anything that osgQt dev's or myself can do other than
> ask you to pay attention when we announce fixes and ask you to fix you
> code.
>
> Robert.
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>
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