[osg-users] Specifying the GL context version to request

[Robert Osfield]

Hi Sandro,

On 21 August 2017 at 15:21, Sandro Mani <manisandro at gmail.com> wrote:

> OpenGL renderer string: Mesa DRI Intel(R) HD Graphics 530 (Skylake GT2)
> OpenGL core profile version string: 4.5 (Core Profile) Mesa 17.2.0-rc4
> OpenGL core profile shading language version string: 4.50
>

Is there a reason why the driver isn't just directly supporting the GL
features that osgEarth is using?  Is the Intel/Mesa driver limiting
features in some way?

Have you tried on an NVIdia or AMD system?

FYI, I'm using NVidia under Kubunty 16.04 as my main build system and
routinely mix latest GL features with just creating a normal graphics
context,


> Are the osgEarth team aware of the issues you've had?
>
> I once asked before investigating [1] but no-one reacted, I suppose they
> are mostly using Windows. Now I have a better understanding of the
> underlying issues (and indeed of what was missing in OSG itself), but
> before reporting issues to the osgEarth team I'd like to understand what
> the correct approach should be (if indeed they are doing something wrong).
>

My guess is that they probably haven't used Linix+Intel with the drivers
that you are using so haven't come across the issue.  Real-time graphics
under Linux has tended to mostly done with NVidia as Intel and AMD have had
sub-standard GL drivers for looooong time.

I suspect it's not really a case of the osgEarth team doing something
wrong, but the Linux+Intel drivers adding a new constraint for keeping
things working sweetly.

I'm starting to wonder if you aren't hitting upon the same issues that
Apple OSG users have had with Apple's decision to only support OpenGL 3+
features on a graphics context without compatibility.  While it seems a
uncontroversial decision at first glance it's ended up being a real pain
for OpenGL users needing to maintain long lived applications that happen to
rely upon both newer features when available as well as old fixed function
pipeline features.  The Apple approach is fine for clean room application
written recently such as new games but crap for the many companies that
develop software that has a useful life that's over a decade long.

Robert.
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