[vtkusers] Animation without polling?

[Mark Gooding]

you shouldn't have to write a complete vtkRenderWindowInteractor, just
add an observe to handle AnimationCueTickEvents

http://www.vtk.org/doc/nightly/html/classvtkCommand.html

i'll try to send you more detailed information later. I don't have my
software which did animation to hand right now.

Mark


2009/9/10 Guido Rodriguez <guidorodriguez1952 at hotmail.com>:
> Dear VTK users/developers,
> I ask for guidance, how animated visualization is done right with VTK. What
> I have in mind is an application which calculates, let's say, a temperature
> field, which changes in time. Whenever the field is completely calculated
> for the next time step, the visualization should be updated. In parallel,
> the user should be able to work with the mouse/key controls to rotate the
> view, zoom, interact with 3D widgets, etc.
>
> The obvious way would be to run VTK in one thread, and the calculation in
> another. Each finished calculation step would notify VTK to update. But it
> doesn't work like this. At least not with the X windows system. When I call
> some pipeline's Update() function from a different thread, I get an "invalid
> thread access".
>
> Next attempt. I implement an event buffer, which is written to by the
> calculation thread, and which is read from by the VTK thread. This works
> like a charm. Now VTK can check whether an update is necessary and get the
> required data from the event buffer. But _when_ does VTK check for updates?
> I can't seem to find a solution which sets VTK to sleep until either a
> mouse/key event happens or until the calculation thread releases some lock,
> simply because any VTK callback waiting for notification from a different
> thread would stop VTK from reacting to mouse/key events during this period.
>
> The only solution I can see is to add a timer event like every 10 ms, which
> checks the event buffer for updates. This works, but is it recommended?
> Threading libraries have introduced locks and notification to avoid the
> overhead from polling at interactive rates for events that may occur only
> every few seconds. How can good multithreading programming styles be applied
> to VTK?
>
> I hope the problem is clear. Can a different thread trigger pipeline updates
> under X windows? Or do I have to write my own vtkRenderWindowInteractor?
>
> Regards,
> Guido
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