[vtkusers] VTK, Python, MacOS X, Cocoa, Offscreen rendering?

[Sean McBride]

On 3/13/08 8:21 AM, Bridgman, William T. said:

>I've found some posts from June 2004 ("Mac offscreen drawing")  
>suggesting that VTK should be able to do offscreen rendering through  
>the Cocoa interface, but that this was not yet implemented.  Has this  
>changed?

I've never used 'offscreen' and to be honest I'm not _exactly_ sure what
it is... :)  But I can suggest some reading for you. :)

>I'm trying to batch export RIB files on an XGrid cluster (Hundreds of  
>files that take 5-15 minutes to process).
>
>I've got vtkPython running with Cocoa but haven't found the sequence  
>of commands that completely disables the window generation.  My  
>simple-minded first guesses of
>
>             renWin=vtk.vtkCocoaRenderWindow()
>             renWin.OffScreenRenderingOn()
>
>before installing actors, die with:
>
>kCGErrorRangeCheck : Window Server communications from outside of  
>session allowed for root and console user only
>INIT_Processeses(), could not establish the default connection to the  
>WindowServer.Abort
>
>when run on the headless machines.  It runs fine without off-screen  
>rendering on a console, though I believe some window briefly  
>appears.  I suspect I'm missing something in the initialization  
>sequence but am not that familiar with Cocoa.

You can read about the 'window server' here:
<http://developer.apple.com/technotes/tn2005/tn2083.html#SECWINDOWSERVER>

and about 'daemon-safe frameworks' here:
<http://developer.apple.com/technotes/tn2005/tn2083.html#SECLIVINGDANGEROUSLY>

Also, maybe add a log or breakpoint to
vtkCocoaRenderWindow::CreateAWindow(), do you reach that point on your
headless Mac?  If so, that would explain your problem.

-- 
____________________________________________________________
Sean McBride, B. Eng                 sean at rogue-research.com
Rogue Research                        www.rogue-research.com 
Mac Software Developer              Montréal, Québec, Canada