That’s what I was asking yes.
I have tried your suggestion and ends up with something like this
This doesn’t look like a slice of the phi field, maybe there is some distortion that has been applied to it ?
What I really want is to extract the angular distribution of fields around the moving sphere. I thought the simplest way to do that was to extract slices in the frame of reference of the sphere, I would then have a series of images where the sphere is in the middle and the scalar field evolves around it until it reaches steady-state, like those aerodynamic simulation of a car that stays still while the air flows move around it.
Maybe this is not the best way to go about it, I could also try to project phi onto a shell type of Glyph, which would be centered on my moving sphere and with a slightly larger radius. Then I could extract it and do angular analysis.
For both solutions there is still the problem of having to duplicate the system on every side to account for periodicity…