1. An image generating system comprising: a first attitude data obtaining unit obtaining first attitude data indicating an attitude of a head-mounted display in first timing; a reference image generating unit generating a reference image shoving a state of looking at a virtual three-dimensional space from a viewpoint, a position and a sight line direction of the viewpoint being identified on a basis of the first attitude data; a second attitude data obtaining unit obtaining second attitude data indicating the attitude of the head-mounted display in second timing subsequent to the first timing; a corresponding position identifying unit identifying a corresponding position for each pixel within a display image to be displayed on the head-mounted display, the corresponding position being a position on a plane including the reference image and being associated with the pixel, on a basis of a difference between the attitude indicated by the first attitude data and the attitude indicated by the second attitude data; a pixel value identifying unit identifying a pixel value of the pixel within the display image, the pixel being associated with the corresponding position, on a basis of one or more pixel values of one or more corresponding pixels within the reference image, the one or more corresponding pixels being selected on a basis of the corresponding position; and a display image generating unit generating the display image on a basis of the pixel value identified for each pixel within the display image; according to presence or absence of the one or mere corresponding pixels within the reference image, the one or more corresponding pixels being selected on the basis of the corresponding position, the pixel value identifying unit controlling whether or not to identify the pixel value of the pixel within the display image, the pixel being associated with the corresponding position, on a basis of one or more pixel values of one or more corresponding pixels within the reference image, the one or more corresponding pixels being selected on a basis of a position on a segment connecting the corresponding position to a position of a reference point within the reference image.