discrepancy when plotting vertex time course with pyvista backend

Describe the bug

The MNE time course looks different when plotting a vertex within the brain visualization GUI via the pyvista backend (top figure shown below) compared to manually plotting the vertex using SourceEstimate.data (bottom figure shown below).

Steps to reproduce

See https://gist.github.com/rythorpe/3c57fdb572bc17bb1f3e4bb70b3e1104 using the somato dataset. Selecting the exact vertex within the brain visualization window can be tricky (unless there is a more controlled way to to this through the API?).

Expected results

I expected the vertex time courses rendered in the GUI to match those plotted manually with matplotlib. Furthermore, I expected the vertex of maximal activity (blue trace shown below) to reflect the largest peak (compared to the orange trace) in the GUI.

Actual results

Note that the blue trace represents the time course of the right hemisphere vertex retrieved with SourceEstimate.get_peak() and that the vertex IDs are the same in each figure.

[jasmainak]

What is the motivation behind plotting the time course for smoothed data by default?

The source space is a decimated surface, so to get a proper visualization you need to smooth the result. You could also plot directly on the source space but since it’s so decimated it will look very weird

[rythorpe]

Thanks for the help @larsoner and @jasmainak!