An image forming apparatus comprising: an engine; an information processing device; an image data acquirer; a color information generator; a height information generator; a corrector; a layer information generator; a conveyance controller; a moving controller; and a builder, wherein the image data acquirer acquires image data representing a three-dimensional image; wherein the color information generator generates, from the image data representing the three-dimensional image acquired by the image data acquirer, color information indicating, on a per-pixel basis, colors of the three-dimensional image; wherein the height information generator generates, from the image data representing the three-dimensional image acquired by the image data acquirer, height information indicating, on a per-pixel basis, heights of the three-dimensional image; wherein the corrector corrects the height information so that surface of the three-dimensional image is covered with the colors indicated by the color information; wherein the layer information generator generates layer information indicating, on a per-layer basis, pixel layouts for building the three-dimensional image whose shape is corrected so that the surface of the three-dimensional image is covered with the colors indicated by the color information, based on the corrected height information and the color information; and wherein the corrector corrects the height information so that the surface of the three-dimensional image is covered with the colors indicated by the color information based on resolution of the three-dimensional image, characterized in that the corrector corrects the height information so as to make a slope angle of a side of the shape of the three-dimensional image substantially equal to an angle of tan -1 ((the height H of a layer)/(the diameter P of the build material in the plane of the layer computed from the inverse of the resolution)). an engine; an information processing device; an image data acquirer; a color information generator; a height information generator; a corrector; a layer information generator; a conveyance controller; a moving controller; and a builder, wherein the image data acquirer acquires image data representing a three-dimensional image; wherein the color information generator generates, from the image data representing the three-dimensional image acquired by the image data acquirer, color information indicating, on a per-pixel basis, colors of the three-dimensional image; wherein the height information generator generates, from the image data representing the three-dimensional image acquired by the image data acquirer, height information indicating, on a per-pixel basis, heights of the three-dimensional image; wherein the corrector corrects the height information so that surface of the three-dimensional image is covered with the colors indicated by the color information; wherein the layer information generator generates layer information indicating, on a per-layer basis, pixel layouts for building the three-dimensional image whose shape is corrected so that the surface of the three-dimensional image is covered with the colors indicated by the color information, based on the corrected height information and the color information; and wherein the corrector corrects the height information so that the surface of the three-dimensional image is covered with the colors indicated by the color information based on resolution of the three-dimensional image, characterized in that the corrector corrects the height information so as to make a slope angle of a side of the shape of the three-dimensional image substantially equal to an angle of tan -1 ((the height H of a layer)/(the diameter P of the build material in the plane of the layer computed from the inverse of the resolution)).