[vtk-developers] OpenGLExtensions not loaded with OffscreenRendering and MultiSamples

[Xabi Riobe]

Hi,

I have an issue (master OpenGL1) with OffscreenRendering if
vtkRenderWindow::MultiSamples > 1.

In vtkOpenGLRenderWindow::CreateHardwareOffScreenWindow there is this test
added 10 months ago by David Lonie:

  // This implementation currently ignores multisampling configurations:
  if (this->MultiSamples > 1)
    {
    vtkDebugMacro(<<"Multisampling is not currently supported by the "
                  "accelerated offscreen rendering backend. Falling back to
"
                  "a platform-specific offscreen solution...");
    return 0;
    }

and that falls back to the
method vtkWin32OpenGLRenderWindow::CreateOffScreenDC.

But in this case, when i enter later
in vtkOpenGLExtensionManager::ReadOpenGLExtensions, i have only 3
extensions loaded, instead of a lot of them when it is
CreateHardwareOffScreenWindow that runs.

A workaround is to set MultiSamples to 0 since it is currently not
implemented, but i am wondering why the extensions are not loaded, and if
something is missing in CreateOffScreenDC.

For information, with OpenGL2 this modification has been commented out with
this note: "the following code causes tests to fail, commenting it out"

Thanks for any information about that.

Xabi
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