Make VR zoom mode not move scene far away

[Tom Goddard]

VR users often zoom scaling the scene bigger and bigger until it clips 100 meters away. They don't realize it is getting bigger and farther away at the same time, so not changing much in apparent size.

To remedy this have VR zooming scale about the center of the scene bounds if the zoom is initiated with cones outside the scene bounds. This will make the scene expand toward the user. If the zoom is initiated with cones in the scene bounds then use the current center point.

[Tom Goddard]

Done.

The zoom center is calculated in the normal way as midpoint between two cones, or tip of single cone for zoom mode, and if that center is outside the scene bounds then the center is replaced with the scene bounds center. Center is fixed at the time the zoom is initiated.