[vtkusers] Problem with parallel rendering

[Matthias Härtel]

Hello!
First, iam relative new to vtk and my english is not the best, so sorry!

Iam working on a program, which shows a dataset of 100 frames as a movie.
The program is almost done, the movie is already playing.
The proceeding of my program is, to read all frames at startup in 
parallel pipelines. So at the end i get a vector of vtkActors, which are 
all added to the display Renderer. This renders all the frames before 
the user can play the movie!

My next wish is, to accelerate the rendering step, cause at the moment, 
the whole rendering is done in one thread frame by frame.
My idea to parallelise the rendering was, to create for example 12 
threads, each with a own renderer and offscreen renderWindow.
Now my problem is, that after the rendering, when the movie begins, vtk 
get an error of "wgl make current". I know this error, but actually, i 
have no idea to fix that!
Can anybody give me some hint, how to parallelise my rendering?

Thanks
Matthias