1. A method performed under control of a game server, comprising: calculating a degree of closeness between a first character and a second character positioned in a same space of a virtual game, based at least in part on a history of mutual activity in the virtual game between the first character and the second character; calculating a level of detail (LOD) for the first character, based at least in part on the calculated degree of closeness; and controlling a display definition of the first character based at least in part on the calculated LOD.