Computer display of curved surfaces

This paper presents a method for producing computer shaded pictures ot curved surfaces. Three-dimensional curved patches are used, a~ contrasted with conventional methods using polygons. The method subdivides a patch into successively smaller subpatches until a subpatch is as small as a raster-element, at which time it can be displayed. In general, this method could be very time consuming because of the great number of subdivisions that must take place; however, there is at least one very useful class of patches-the bicubic patch-that can be subdivided very quickly. Pictures produced with the method accurately portray the shading and silhouette of curved surfaces. In addition, photographs can be "mapped" onto patches thus providing a means for putting texture on computer generated pictures.