Methods, systems, apparatus, and computer program/software code products, operable in a computer graphics system designed to render images and to apply shading to images, enable the following: during rendering of an image, modifying the shading normal in the region of a corner of an object in the image, such that when shading is applied to the image, the shaded image is capable of providing to a human viewer, when viewing the corner in the image, the appearance or visual illusion of a rounded corner, wherein the modifying comprises: calculating an amount of modification to be applied to an original shading normal in the region of the corner to simulate the appearance of a given fillet radius R, the calculating comprising: interrogating surfaces within a distance R of the corner for their shading normal, and calculating a new normal that is a weighted blend between the shading normal of the original surface and the shading normal of the interrogated neighboring surface, thereby, by the shading effect, to simulate at render-time a rounding by varying the shading normal, creating a variation of the surface normal consistent with the appearance the object would have had, had it actually been rounded.