[vtkusers] Interaction with chart on top of 3D (on top of volume rendering?)

[Elvis Stansvik]

Hi all,

At the moment I have a button in my Qt UI that pops up a dialog with a
render window containing vtkChartXY with some points items to control
the transfer functions I use for rendering volumes in another window.

I've been toying with the idea of adding a VTK button (say in the
bottom left corner) in the window where I do the actual volume
rendering, and have that button bring up the vtkChartXY in the same
window (on top of the volume rendering), for more convenient / quick
access to transfer function editing.

I had a look at this test:

    https://github.com/Kitware/VTK/blob/master/Charts/Core/Testing/Cxx/TestChartsOn3D.cxx

It shows a cube with a chart on top in the same renderer.

Would this example work if the cube instead was a volume rendering?

Is it possible to get interaction with the chart working seamlessly
with interaction with the camera?

Is there some other approach that would allow these two things?
Multiple renderers? Has anyone done such a thing?

Thanks in advance,
Elvis