uint32 PackedRelativeBox
When non zero, this represents the relative box used to compute Bounds, using the component bounds as reference. If available, this allows the renderable asset streamer to generate the level streaming data before the level gets visible. At that point, the component are not yet registered, and the bounds are unknown, but the precompiled build data is still available. Also allows to update the relative bounds after a level get moved around from ApplyWorldOffset.