[vtk-developers] Correct handling of information propagation
brad.king at kitware.com
Wed Jan 19 11:49:58 EST 2005
John Biddiscombe (CSCS) wrote:
> Ken Martin wrote:
>> If bounds are not provided then
>> you must go with some default extent.
> If there's no information because the filters haven't generated data
> yet, (ie no bounds available), and a default value is not feasible (just
> can't be guessed sensibly), is it safe to update the inputs during the
> request information call and get the correct sizes? This is what I used
> to do, but I am not sure if the new pipeline will like it.
One of the design principles of the new pipeline is that a filter should
be able to satisfy a request sent to its ProcessRequest method without
being aware of the executive or the pipeline at all. It should work
only with the information passed to this method's arguments. Therefore
it is invalid to try to update the inputs during REQUEST_INFORMATION.
Something will produce an error message and the update will fail.
What you have here is a filter that can't compute its whole extent until
the REQUEST_DATA pass (Execute). Currently we deal with this by
producing a fake whole extent (something like 0 0 0 0 0 0) during
REQUEST_INFORMATION and then correcting it during REQUEST_DATA.
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