[vtk-developers] changes in temporal support in VTK

[Yuanxin Liu]

Hi,
  We are currently considering a few backward-incompatible changes to the
temporal support in the VTK pipeline and would like to hear comments.  We
are also interested in hearing other suggestions to improve handling of
time-dependent data.

  The main change is to remove the use of vtkTemporalDataSet and to limit
the time request to be a single time step, i.e.

   - Currently, a filter can request objects from multiple time steps by
   setting the key UPDATE_TIME_STEPS to a vector of doubles; the resulting
   objects get wrapped by the pipeline into a single vtkTemporalDataSet object.
   - After the change, a filter can only request a single time step by
   setting the key UPDATE_TIME_STEP to a single double.  The "wrapping" no
   longer happens.

  For existing filters that depend on multiple time steps,  we will modify
them to use the CONTINUE_EXECUTION key to iteratively execute the pipeline
and store the objects from the iterations.   There will be super
classes/utility classes to make this easy.

  The main motivation is that, by pushing the temporal functionality from
the core pipeline to the filters, the execution pipeline becomes simpler
and easier to maintain. Some bugs, e.g.( ParaView bug
Id=6662<http://www.paraview.org/Bug/view.php?id=6662>)
will go away as a result.

Leo
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