Below Cesium's trackball height (7,500 km by default) a drag that starts
on the stars turns the camera in place, whatever enableLook says, which
was the drag path to a view with no planet in it. Lower that height to
the free-look height with the free-look limit, never raising it, and
restore it on dispose. Above 1,000 km such a drag now orbits the globe,
as it already did above 7,500 km, at a similar rate, and a tilt drag
from the stars there tilts about the planet's edge or does nothing
instead of turning the camera. Drags that start on the planet are
unchanged.