| 摘要 |
PURPOSE:To improve a processing speed by detecting a face at the rear side of an object by a sign of the (z) direction component of a normal vector and omitting the calculation of the depth coordinates and the comparison as to the rear side face. CONSTITUTION:Coordinates of each apex of, e.g., a face P1 are fed to a normal vector operating circuit 6 from a terminal input. Then the polarity of the (z) direction component of the normal vector is operated. Since this value is negative, the coordinates are calculated by a z coordinate operating section 1 as to each picture element of the face P1, converted into picture elements and fed to a comparator 5. The comparator 5 compares them with the maximum value of (z) direction read from a Z buffer 2 and since the (z) coordinate value of the picture element calculated is smaller naturally, the depth corresponding to x, y coordinates of each picture element, e.g., (z) coordinate is written in the Z buffer 2. When the polarity of the (z) component is positivae, that is, in case of a face P2, no operation of the Z coordinate operating section 1 is conducted and no comparison by the comparator is conducted. In case of an overlapped object, the (z) coordinate of faces in the visual point direction is compared. |
