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

Claim 1

A shading circuit for shading a plurality of triangular polygons which constitute a solid model to be displayed on a screen defined by orthogonal coordinate axes X and Y, characterized by comprising: preprocessing means (l5), connected to receive three items of vertex data which each contain the intensity and X, Y and Z coordinates of a corresponding vertex of a triangular polygon, for specifying the value in Y coordinate as one of scan lines which are parallel to the coordinate axis X and intersect the polygon, obtaining intensities and depth or Z coordinates of two points located at the positions where said one scan line intersects sides of the polygon, and obtaining the change ΔI/ΔX of intensity for each unit change in X coordinate and the change ΔZ/ΔX of Z coordinate for each unit change in X coordinate, based on the intensities and Z coordinates of said two points; and shading section (l6), connected to receive the vertex data items and the changes ΔI/ΔX and ΔZ/ΔX, for sequentially obtaining intensities and Z coordinates of points on a side of the polygon as starting intensities and starting Z coordinates for said scan lines, and sequentially obtaining intensities and Z coordinates of points inside the polygon for each scan line, based on the corresponding starting intensity and the correspond­ing starting Z coordinate and commonly on the changes ΔI/ΔX and ΔZ/ΔX.

Claim 7

A method for shading a plurality of triangular polygons which constitute a solid model to be displayed on a screen defined by orthogonal coordinate axes X and Y, characterized by comprising: a first step of preparing three items of vertex data which each contain the intensity and X, Y, and Z coordinates of a corresponding vertex of a triangular polygon; a second step of specifying the value in Y coor­dinate as one of scan lines which are parallel to the coordinate axis X and intersect the polygon and obtain­ing intensities and depth or Z coordinates of two points located at the positions where said one scan line inter­sects sides of the polygon, based on said vertex data items; a third step of obtaining the change ΔI/ΔX of intensity for each unit change in X coordinate and the change ΔZ/ΔX of Z coordinate for each unit change in X coordinate, based on the intensities and Z coordinates of said two points; and a fourth step of sequentially obtaining intensities and Z coordinates of points on a side of the polygon, as starting intensities and starting Z coordinates for said scan lines, based on the vertex data items, and sequen­tially obtaining intensities and Z coordinates of points inside the polygon for each scan line, based on the corresponding starting intensity and the corresponding starting Z coordinate and commonly on the changes ΔI/ΔX and ΔZ/ΔX.

Claim 8

A method for shading a plurality of triangular polygons which constitute a solid mode to be displayed on a screen defined by orthogonal coordinate axes X and Y, characterized by comprising: a first step of preparing three items of vertex data which each contain the intensity and X, Y, and Z coordinates of a corresponding vertex of a triangular polygon; a second step of obtaining the change ΔI/ΔX of intensity for each unit change in X coordinate and the change ΔZ/ΔX of depth or Z coordinate for each unit change in X coordinate, based on the following equations: (ΔI/ΔX)Y: constant = {(Yl-Y2)(I2-I3)-(Y2-Y3)(Il-I2)} /{(Yl-Y2)(X2-X3)-(Y2-Y3)(Xl-X2)} (ΔZ/ΔX)Y: constant = {(Yl-Y2)(Z2-Z3)-(Y2-Y3)(Zl-Z2)} /{(Yl-Y2)(X2-X3)-(Y2-Y3)(Xl-X2)} where Xl, X2, and X3 are respectively the X coordinates of three vertexes A, B, and C of the polygon; Yl, Y2, and Y3 are respectively the Y coordinates of vertexes A, B, and C; Zl, Z2, and Z3 are respectively the Z coor­dinates of vertexes A, B, and C; and IL, I2, and I3 are respectively the intensities of vertexes A, B, and C; and a third step of sequentially obtaining intensities and Z coordinates of points on a side of the polygon, as starting intensities and starting Z coordinates for scan lines parallel to coordinate axis X, based on the vertex data items, and sequentially obtaining intensities and Z coordinates of points inside the polygon for each scan line, based on the corresponding starting intensity and the corresponding starting Z coordinate and commonly on the changes ΔI/ΔX and ΔZ/ΔX.