Graphic display apparatus with improved shading capabilities

Claim 1

A graphic display apparatus comprising: geometry transforming means for inputting graphic data of a target object and transforming the graphic data into coordinate values of a device coordinate system which is used by the graphic display apparatus; area calculation means, coupled to said geometry transforming means, for calculating an area of a particular polygon that is formed by the transformed coordinate values of the device coordinate system; shading technique selection means, coupled to said geometry transforming means, for selecting a shading technique corresponding to the area of the particular polygon calculated by said area calculation means from a plurality of shading techniques which are determined in advance depending upon the calculated area, said shading technique selection means selecting a shading technique which enables a first degree of realistic representation when the area of the polygon calculated by the area calculation means is larger than a threshold value, and selects a shading technique with a second degree of realistic representation, lower than said first degree of realistic representation, when the area of the polygon calculated by the area calculation means is not larger than the threshold value; luminance calculation means, coupled to said shading technique selection means, for calculating a luminance of the graphic data of the target object according to the shading technique selected by said shading technique selection means for the particular polygon; and dot developing means, coupled to said luminance calculation means, for developing the graphic data of the target object for which the luminance is calculated by said luminance calculation means into dots.