Upon projecting the inside of a virtual space on a prescribed projection plane and generating a two-dimensional image, foremost, the relative position of the operational unit and the relative direction designated with such operational unit are acquired, and these are substituted with the position and direction in the virtual space. Next, the position of the operational unit in the virtual space is shifted a prescribed amount horizontally and/or vertically to set the starting point, and an ending point is set on a virtual line extending along the direction designated by the operational unit in the virtual space. Next, a virtual viewpoint which approximately matches the position and direction of the operational unit in the virtual space is set and subject to projective transformation, and a two-dimensional image containing the trajectory image corresponding to a part or the entirety of the zone connecting the starting point and ending point is generated thereby.