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

[Marcus D. Hanwell]

On Fri, Sep 23, 2016 at 1:36 AM, Elvis Stansvik
<elvis.stansvik at orexplore.com> wrote:
> 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.

Yeah, I added that.
>
> Would this example work if the cube instead was a volume rendering?

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

No, this is something I was hoping to revisit but I could not get the
interaction events to switch from the 2D scene to the 3D. This was my
ideal, and what I had in mind when writing the test.
>
> Is there some other approach that would allow these two things?
> Multiple renderers? Has anyone done such a thing?
>
Not that I know of, if they have I would love to see how they achieved
it. I think the main obstacle is getting the interaction events to the
2D or 3D interactor observer depending upon where the mouse is. I
don't think it is that hard, but we never had a project pushing for
it. The widgets do something on this level, where they intercept the
events when they are in an active region so that is probably a good
place to go looking.