A portable electronic system comprising: a sensor (51, 52) configured to capture three-dimensional information about objects in a physical world; an active memory; a local memory; a transceiver configured for communication over a computer network with remote memory; and a processor communicatively coupled to the sensor (51, 52), the active memory, the local memory, and the transceiver, and configured to execute computer executable instructions to provide a 3D representation of a portion of the physical world based at least in part on the 3D information about the objects in the physical world, wherein: the 3D representation of the portion of the physical world comprises a plurality of blocks (3102, 3104, 3106, 23108), each block having values representing objects in a region of portion of the physical world at a point in time, including location information with respect to the physical world; and the computer executable instructions comprise instructions for: persisting the plurality of blocks (3102, 3104, 3106, 23108) in at least one of the active memory, the local memory and the remote memory when the portable electronic system changes to an inactive operation status at a first time; upon a transition to an active status at a second time, after the first time, selecting, from the persisted blocks, blocks that represent portions of the physical world around the portable electronic system at the second time; and rendering, based at least in part on the selected blocks, virtual content to a user of the portable electronic system. a sensor (51, 52) configured to capture three-dimensional information about objects in a physical world; an active memory; a local memory; a transceiver configured for communication over a computer network with remote memory; and a processor communicatively coupled to the sensor (51, 52), the active memory, the local memory, and the transceiver, and configured to execute computer executable instructions to provide a 3D representation of a portion of the physical world based at least in part on the 3D information about the objects in the physical world, wherein: the 3D representation of the portion of the physical world comprises a plurality of blocks (3102, 3104, 3106, 23108), each block having values representing objects in a region of portion of the physical world at a point in time, including location information with respect to the physical world; and the computer executable instructions comprise instructions for: persisting the plurality of blocks (3102, 3104, 3106, 23108) in at least one of the active memory, the local memory and the remote memory when the portable electronic system changes to an inactive operation status at a first time; upon a transition to an active status at a second time, after the first time, selecting, from the persisted blocks, blocks that represent portions of the physical world around the portable electronic system at the second time; and rendering, based at least in part on the selected blocks, virtual content to a user of the portable electronic system. the 3D representation of the portion of the physical world comprises a plurality of blocks (3102, 3104, 3106, 23108), each block having values representing objects in a region of portion of the physical world at a point in time, including location information with respect to the physical world; and the computer executable instructions comprise instructions for: persisting the plurality of blocks (3102, 3104, 3106, 23108) in at least one of the active memory, the local memory and the remote memory when the portable electronic system changes to an inactive operation status at a first time; upon a transition to an active status at a second time, after the first time, selecting, from the persisted blocks, blocks that represent portions of the physical world around the portable electronic system at the second time; and rendering, based at least in part on the selected blocks, virtual content to a user of the portable electronic system. persisting the plurality of blocks (3102, 3104, 3106, 23108) in at least one of the active memory, the local memory and the remote memory when the portable electronic system changes to an inactive operation status at a first time; upon a transition to an active status at a second time, after the first time, selecting, from the persisted blocks, blocks that represent portions of the physical world around the portable electronic system at the second time; and rendering, based at least in part on the selected blocks, virtual content to a user of the portable electronic system.