Describe the problem

In #8190, @larsoner suggests that we can add 3D translucent brain visualization of a time series for depth electrode data (i.e. SEEG).

Describe your solution

"if we improve stc_near_sensors to allow returning a VolSourceEstimate object then nothing new needs to be done at the viz end. In other words, we "just" need to come up with a suitable way to interpolate the sEEG sensor activity into a volume, and once that's done, stc.plot and stc.plot_3d should just work."

Seems like the work in sequence comprises of:

1. make stc_near_sensors allow to return a VolSourceEstimate object
2. make stc_near_sensors have an interpolation scheme for SEEG sensor data into a 3D volume (possibly say just via 1/r^2 propagation?)
3. possibly add SEEG example showing stc.plot and stc.plot_3d similar to how Eric has done in MRG, ENH: ECoG plotting on pial #8190

Any other suggestions to the above are appreciated! Will try to tackle this soon.

Describe possible alternatives

TBD

Additional context

Logging this as an issue, to not forget the conversation Eric brought up.