A method and an apparatus for generating an image with shallow depth of field, suitable for a three-dimensional imaging system having a left lens and a right lens, are provided. In particular, a memory read request that has been speculatively issued to a lower memory level prior to completion of a cache lookup operation initiated in a cache memory in a higher memory level may be reordered ahead of at least one previously received and pending request awaiting communication to the lower memory level. A weatherable layer comprising a layer of a weatherable material covers an upper surface of the reflective layer. Thereby the air inflation device is useful and practical. In this manner, passive and active systems are integrated within a single, convenient layer that possesses the best features of both active systems and passive systems. The cover also has a means for releasably attaching the cover to a seating unit.