[vtkusers] New pipeline and interpolation between time steps.

[Wiktor Moskwa]

Hello,

I'm writing a reader for VTK and I decided to make use of
a new pipeline architecture. My goal is to interpolate data
between time steps and I've chosen a following way to do it:

My data consists of several time steps, each with its time
value. In a request information phase
vtkStreamingDemandDrivenPipeline::TIME_STEPS()
is set and particular time step can be loaded by setting
vtkStreamingDemandDrivenPipeline::UPDATE_TIME_INDEX().

Next I'm going to write a filter with a method
SetTimeValue() that can interpolate its input data in this way:
- obtain as many time steps as needed from underlying reader
by setting UPDATE_TIME_INDEX() in a loop
(vtkStreamingDemandDrivenPipeline::CONTINUE_EXECUTING())
- interpolate data set to this->TimeValue.

Of course interpolation filter doesn't depend on a specific
reader and could be used with connection to any vtkAlgorithm
that provides time steps.

There is vtkInterpolateDataSetAttributes filter but it requires
multiple input and is not comfortable to use.

I know that time support is under development in VTK, but
I'd like to know if this reader and possibly a filter fits
well in a design of time support in VTK. Or maybe I'm doing
something completely wrong.
Any suggestions will be appreciated.

Regards,
Wiktor Moskwa