This is called prior to the updating of the vcam's child cameras, in order to allow the parent to prepare its children. If the children are updating on FixedUpdate, then this will not necessarily be called prior to every FixedUpdate, but it might be called on LateUpdate instead.

void PreUpdateChildCameras(
	Vector3 worldUp,
	float deltaTime
)

function PreUpdateChildCameras(worldUp, deltaTime);