Arcball jittery at far distances

[kephale]

Describe the bug

When you're zoomed out (tested in sciview) the scene becomes jittery when you interact with it, see:

jittery_arcball_scenery.mp4

To Reproduce

Testing on scenerygraphics/sciview#532 (but i think the same thing should happen on main it just takes more time to zoom out far enough), just using an empty scene, zoom out and see the above behavior

Expected behavior

No jitter

Desktop (please complete the following information):

• OS: MacOS

[odinsbane]

I tried this on main and I get the same issue one windows 10. It's a bit strange, when I zoom out everything is fine, then suddenly it switches and gets jittery. Then, I cannot zoom back in.

The camera position changes abruptly from ~500 to 6900 and then it gets jittery. If I try to zoom back in it is really slow. As though it makes a huge jump around 500 then goes back to normal scrolling rate if I try to zoom back in.

On a related note, if I set the position of the "DetachedHeadCamera-0" then a wireframe sphere appears, I'm not sure how to manage it's visibility. I can add an issue if it is something of concern.