Animating plots?

[TomNicholas]

Is there a way to animate data? Even just with some kind of callback to an external function which resupplies the new data for the next timestep?

[TomNicholas]

I noticed that if I create an isosurface I can then alter it with

list(plot.objects)[0].scalar_field = new_scalar_field

If I created a data object which changed in response to an external widget, would this be a good way to animate 3D plots? Or would it likely be too slow?

[TomNicholas]

Oh in this example there is a widget to update the plot, so presumably I can do something similar even without invoking VTK?

[marcinofulus]

Dear Tom,

We have basically two possibilities:

• backend driven animation: to use widgets to communicate data each timestep (as in your issue)
• frontend animation - use a new feature which is working for some plot objects - namely to sent dictionary with { '0.1': array1, '0.2': array2,....} - it will send to frontend timeseries and playback will bo possible in purely javascript - even without frontend.

But - the point is that not all objects accept timeseries. Look into code e.g. l

• lines do https://github.com/K3D-tools/K3D-jupyter/blob/1f6155d8f90a644854a54e70904afe488954e1ba/k3d/objects.py#L241
• but marching-cubes do not. The reason is that marching cubes do CPU intensive computations every time dataset or level is updated, on frontend - javascript.

Thus for your case I would suggest:

• use backend driven animation if the speed is ok for you.
• use volume rendering instead marching cubes - computations are purely on webgl side, and we support timeseries. You might need to edit transfer function to have "almost" isosurface effect.
  • compute isosurfaces for the whole timeseries on the backend, and send it to mesh object (you will need vertices and indices arrays). This will give you probably the fastest animation.

If you send me more information on the dataset or example notebook, I can give you some more specific advices.

[TomNicholas]

Thanks for explanation @marcinofulus !

Ideally I would like the simplest interoperability possible between the animate widget and the K3D plot, so I guess what I should do is wait for #191 to be closed (is there a corresponding pull request anywhere which I could check out?), and have a go with that first.

[marcinofulus]

All of those scenarios are the same simple or complex, but they are different. 2.7.2 is out so plot.auto_rendering = False works now.

[tgandor]

@TomNicholas - can we close this?

[TomNicholas]

Yes - I'll reopen when I have more specific difficulties.

On Thu, 26 Mar 2020 at 12:27, tgandor notifications@github.com wrote:

@TomNicholas https://github.com/TomNicholas - can we close this?

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[etienne87]

is there an example where we can move the camera and fetch some snapshots, offline ?