[vtkusers] VTK time support - how good is it?

[Johannes Töger]

Hi!

Our research group is considering using VTK (or some higher-level library
like Mayavi/TVTK) for visualization of blood flow in the heart. Data is
available as three-dimensional, time-resolved velocity fields measured using
Phase Contrast MRI. Additionally, we have animated anatomical slices of the
heart.

All datasets are sampled over one heart beat (or a part of the heartbeat for
technical reasons), but with different timesteps. For example, the velocity
data might have 40 timesteps and the anatomical slices 25 or 30.

This data is inherently time-resolved, so good time support is a must. I've
been reading a lot about the time support in VTK, but the only thorough
description I can find is an old(?) wiki post from when it was first
discussed: http://www.vtk.org/Wiki/VTK/Time_Support .

One paragraph in this article is particularly interesting:

"Playback of an animation means varying *time*, instead of varying *
timesteps*. By sampling time at regular intervals, animations can play-back
at the correct rate, even if the timesteps in a dataset don't represent
regular intervals. When dealing with multiple datasets, the correct data can
automatically be displayed, as long as the dataset timesteps share a common
reference (if they don't, simple offset and scale transformations are
trivial to implement and use). In the case of a single dataset, matching the
animation sample points to the timesteps in the dataset can provide
backwards-compatible behavior."

Now to my questions:

* Is time support indeed this general in VTK?

* Does it work seamlessly with the rest of VTK?

* Is there a performance penalty when working with timesteps? If so, how
large is it?


Thank you for your attention,

Johannes Töger
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