An apparatus is disclosed. The apparatus comprises an optical sensing system that comprises at least one camera, the at least one camera being configured to acquire an image of a physical environment. The apparatus further comprises a processing system. The processing system comprises an orientation and position determination module configured to detect salient features from the image, and determine a change in orientation and/or position of the apparatus with respect to the physical environment based on the detected salient features. The processing system also comprises a rendering module configured to determine a rendering of the physical environment based on the image and on the determined change in orientation and/or position of the apparatus, and provide data related to the rendering of the physical environment to a display system.