[vtk-developers] OpenGL Extension loading with OSMesa?

[burlen]

On 04/17/2013 09:22 AM, Kevin H. Hobbs wrote:
> On 04/17/2013 11:30 AM, burlen wrote:
>> Hi Utkarsh,
>>
>> It's almost working, there's a test in the extension manager that always
>> fails when using software rendering, for OS Mesa tests for any and all
>> extensions fail weather they're actually support or not. The comment on
>> this test says it has to do with nvidia driver over ssh -X and mentions
>> a ParaView bug but doesn't say which one. Are you familiar with that
>> issue? Although nvidia is mentioned the comment, the test doesn't
>> differentiate between nvidia and other vendors.  I pushed a patch on
>> Gerrit that lets OS Mesa report it's true
>> capabilities(http://review.source.kitware.com/#/c/10927/). Could you
>> take a look?
>>
> This build uses the patch and OSMesa :
>
> http://open.cdash.org/buildSummary.php?buildid=2878607
>
> and has OpenGL 2.1 features.
>

Hi Kevin,

Tests that make use of classes that require extensions pass silently 
when the extensions aren't present, thus the fact that the dashboard is 
green doesn't mean a whole lot in this case. With Utkarsh's patch the 
extension manager is now correctly loading the extension string and 
appending supported versions. However, tests for specific open gl 
versions are hardwired to fail when software rendering is used. Take a 
close look vtkOpenGLExtensionManager::ExtensionSupported implementation.

Version tests are used ubiquitously in VTK for example take a look at 
vtkTextureObject::IsSupported implementation. In Mesa 9.1.1 all of the 
required extensions needed by the texture object are available, however 
it's not working because the version test fails.

Hope that clarifies things
Burlen