Shading circuit for shading a plurality of polygons which constitute a solid model, and method of shading the same

摘要

A shading circuit has a unit for calculating coordinates and intensities of points inside a polygon based on X, Y, and Z coordinates and intensities of vertexes of each of polygons constituting a solid model. This unit includes a preprocessing section for obtaining the depth change &Dgr;Z/&Dgr;X of Z coordinate for each unit change in X coordinate and the change &Dgr;I/&Dgr;X of intensity for each unit change in X coordinate, based on X, Y, and Z coordinates and intensities of three vertexes of each of triangular polygons constituting a solid model, and a digital differential analyzer until for obtaining Z coordinates and intensities of points inside each polygon commonly using . DELTA.Z/&Dgr;X and &Dgr;I/&Dgr;X when the X and Y coordinates of the points are determined.