tl;dr: How do I get the distance from the camera to the globe (preferably to the nearest point on the surface, else the centre)?
I've been playing around with Cesium for only a couple of hours now, but I very much like what I'm seeing. I just received my Leap Motion in the mail today, and was inspired by <a href="http://blog.leapmotion.com/post/55639018480/leapinto-google-earth">Google Earth</a> to support hand-wavey input to fly the camera around.
I've made a basic start and am pretty happy so far. However I need to be able to move slower the closer I get to the surface, and for that I need to know how far away the surface is. From reading the docs, the closest I got was CameraController.getMagnitude(), but that seems to vary wildly over time, and I'm not exactly sure which vector it's measuring.