The bounding box is 2D because it is the bounding box for clipping after the projection. There is no camera position in axonometric projection, only a direction and a 2D bounding box for clipping. It is enough to clip the result after the projection,...

Calling GetBounds () on the axonometric camera tells you the bounding box of the region that should be displayed. The center of the view is the center of this bounding box. Hope this helps, Zoltan