A data structure includes variable-size data objects ["VSDOs"] and enables selective and efficient retrieval of data in particular VSDOs. The data structure includes multiple packets. Each packet includes a reference count field, a references field, and an objects field. The references field stores references to VSDOs within the data structure. The reference count field indicates the number of references stored in the references field. The objects field stores the-actual VSDOs. To access a particular VSDO, an accessing unit traverses the reference count fields of the multiple packets until the accessing unit finds a packet that includes the reference to the particular VSDO. The accessing unit accesses the particular VSDO based upon the reference. To further improve the efficiency of an access operation, packets form metapackets. A metapacket header sums the reference count fields of the packets within the metapacket. To access a particular VSDO, an accessing unit traverses the metapacket headers until the accessing unit finds a metapacket that includes a packet having the reference to the particular VSDO. Based upon the reference, the accessing unit accesses the particular VSDO. Storing light field information in VSDOs using the data structure facilitates efficient light field operations and light field operations at selective levels of refinement.