1. A subpixel rendering apparatus, comprising: a position determination unit configured to determine positions of eyes of a user; and a subpixel determination unit configured to determine, based on the positions of the eyes, a subpixel, among subpixels forming a three-dimensional (3D) pixel, the subpixel emitting a ray that enters the eyes, wherein the subpixel determination unit determines the subpixel based on horizontal direction information of a virtual line connecting the 3D pixel to the eyes, and wherein the horizontal information comprises a horizontal direction slope of the virtual line.