How to set "off_screen" totally? about pyvistaqt

[GuillaumeFavelier]

First off it's called off_screen but there might be a better name for it. AFAIK, except if VTK itself is built to support this feature (for example osmesa: https://discourse.vtk.org/t/offscreen-rendering-opening-window/1660/2, https://discourse.vtk.org/t/black-image-when-using-offscreen-rendering-inside-qt-application/3935), a "screen" will be needed. This screen can be virtual that's why our CIs on Linux use xvfb for instance.

So off_screen=True in pyvistaqt is more about "rendering without opening a window". Also from my experience, this mode has limitations but I can investigate further if necessary.

Now back on your question, I don't quite understand the link between off_screen and view_isometric. The latter just set the default camera parameters. Those can be modified exactly like the vanilla Plotter in PyVista by playing with the camera attribute. Do you have an issue with it?

[szsdk]

So off_screen=True in pyvistaqt is more about "rendering without opening a window". Also from my experience, this mode has limitations but I can investigate further if necessary.

Now, I have a better understanding about the off_screen flag. In the beginning, The update method of BasePlotter

https://github.com/pyvista/pyvista/blob/fbb8570ebd942cdb82a0602daf78a8dff9e2c972/pyvista/plotting/plotting.py#L1166-L1180

gives me a wrong idea that off_screen is used for avoiding rendering. And this is why I found it a little bit strange when I saw view_isometric triggers a rendering at

https://github.com/pyvista/pyvista/blob/fbb8570ebd942cdb82a0602daf78a8dff9e2c972/pyvista/plotting/plotting.py#L836-L843

[GuillaumeFavelier]

Good catch.

So when off_screen=True, the update() function is disabled because it depends on an internal attribute called self.iren (of type vtkRenderWindowInteractor) which is not initialized. This is arguably the limitation I'm talking about in mne-tools/mne-python#8602 (comment).

But the rendering window itself (attribute self.ren_win of type vtkRenderWindow) can still be used for rendering.

I hope what I say is not too confusing, sorry for going into details.

[szsdk]

Thanks for your detailed explanation. I am doing some development on a remote server. Sadly, My Mac does not cooperate well with it. And I cannot make pyvistaqt work through ssh. So I hope I could run some off screen test at least. But now it seems to be another died end. So according to your link, there would be a big refactor of pysitaqt?

[szsdk]

Please feel free to close this issue.

[GuillaumeFavelier]

So according to your link, there would be a big refactor of pysitaqt?

No this part is not related to pyvistaqt sorry 😅