title: How to enable vtk "direct" hardware rendering, X11 / Ubuntu 11.04 x86-64?
body: <p>I notice that the <code>IsDirect()</code> method which should say whether hardware rendering is on returns false on my vtkRenderWindow*, link to class doc:
  <a href="http://www.vtk.org/doc/nightly/html/classvtkRenderWindow.html" rel="nofollow">http://www.vtk.org/doc/nightly/html/classvtkRenderWindow.html</a></p>
  
  <p>How do I enable it? Seems like a build option in cmake should do it, but what? My OpenGL libs are found OK. I notice there's a thread from a while back here: <a href="http://www.vtk.org/pipermail/vtkusers/2005-July/081034.html" rel="nofollow">http://www.vtk.org/pipermail/vtkusers/2005-July/081034.html</a>   but I don't see any more recent info so far, is it just not supported on Linux? </p>