The perspective image of an infinite checkerboard. It can be constructed starting from any triangle Δ O X Y, where O X and O Y form the near corner of the floor, and X Y is the horizon. If O Y_1 P_(1, 1) X_1 is the corner tile, the lines Y_1 P_(1, 1) and P_(1, 1) X_1 must be parallel to O X and O Y respectively. This means that in the drawing they will meet O X and O Y at the horizon, i.e., at point X and point Y respectively. This property, of course, extends to the two bunches of perpendicular lines forming the grid.