| 摘要 |
PURPOSE:To attain the clipping of a three-dimensional object by suppressing a frame buffer updating by a shading means in accordance with the compared result of the Y coordinates of a point on a clipping surface corresponding to the X coordinates of a painted-out object point and the Y coordinates of the painted-out object point. CONSTITUTION:By obtaining the arbitrary clipping surface perpendicular to an X-Y plane as the equation of the straight line on an X-Y plane, Y coordinates of the point on the clipping surface corresponding to the X coordinates of the painted-out object point are obtained by the operation of a simple expression (Y=aX+b) from the X coordinates. By comparing the Y coordinates obtained by the operation with the Y coordinates of the painted- out object point by a comparing means 16, it can be discriminated whether or not the corresponding point is the point which is the object of the clipping. Then, in accordance with the compared result of the comparing means 16, the frame buffer updating due to a shading means 13 is suppressed. Thus, the clipping of the three-dimensional object due to the clipping surface only perpendicular to the X-Y plane can be performed. |
