ArrayCamera rotation support (including OrbitControls.js)

[alxdncn]

It would be great to be able to rotate an array camera as you would a regular camera, i.e. either accessing it's .rotation property or passing the camera into an orbit controls script. While this isn't particularly valuable for VR applications, any other type of application that leverages the optimization possible through ArrayCamera has to do a lot of workarounds to make rotation function properly.

[alxdncn]

I was able to solve this by copying the main camera's rotation to each of the subcameras every frame, but that seems a little circuitous.

[Mugen87]

@mrdoob We have a few issues regarding ArrayCamera where people expect this class behaves like other camera classes.

I think ArrayCamera should focus on what it does in context of XR. Meaning providing the possibility for single-pass rendering. So stuff like updating render lists and states or shadows is done only once when using ArrayCamera.

Have you considered to make the class internal and not expose it to users? One could consider to change its name and not derive it from PerspectiveCamera (so that it is not a 3D object).