Portable device, virtual reality system and method

A portable device comprises a viewing direction sensor configured to determine the viewing direction of a user of the portable device in the real world and a position determiner configured to determine a position of the user in the real world. Furthermore, the portable device comprises a processing unit configured to generate - based on the viewing direction of the user and the position of the user in the real world - a virtual world in which a change of the viewing direction in a 3D coordinate system of the real world leads to a change of the viewing direction in a 3D coordinate system of the virtual world. The portable device further comprises a display configured to display the generated virtual world to the user while blocking a view of the real world.