[vtkusers] MPI Offscreen Volume Rendering

[John Biddiscombe]

> I finally figured out that John Biddiscombe was right that I should not
> be using the vtkDistributedDataFilter. I think I should be using
>   
I'm not sure it's really the answer. Although I didn't say anything 
wrong, I was in a hurry and hadn't apprecaited from reading your message 
fully that you are volume rendering */unstructued grids/* (as opposed to 
imagedata). The trouble is that when you read "pieces" from a file, you 
will end up with chunks "randomly arranged" in space and rendering each 
chunk on a separate node will give you compositing nightmares because of 
the depth sorting issue. In this case perhaps Distributed Data Filter 
will help you (it's not one I've used directly so won't comment)

Now ideally the Reader would be able to accpet a "piece" description 
which was a bounding box in space, the master controller would query the 
file, and get the bounding box of everything, you could subdivide space 
into regions, read regions into each process as pieces and then render 
non overlapping using back to front sort on the top level actor objects. 
All would be fine.

I've not followed all this thread very carefully as I'd assumed you'd 
solved the data trouble and were having rendering trouble of an 
unrelated matter. I'm not entirely certain what it is you are trying to 
do that isn't working.

(ie I'm not helping am I!)
JB

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