PURPOSE:To quicken a cross-sectional view display simply by providing a 1st interpolation means for applying linear interpolation of a drawn picture and a 2nd interpolation means for applying linear interpolation to a difference between a (z) value of a truncated plane and a (z) value of an end point to control whether or not the picture is to be drawn at each pixel based on a discrimination signal. CONSTITUTION:The 1st interpolation means 1, 5, 6, 7 apply linear interpolation of a drawn picture. Moreover, the 2nd interpolation means 3, 15 applies linear interpolation to a difference between the (z) value of the truncated plane calculated by the coordinate of an end face of the drawn picture based on a truncated equation and the (z) value of the end point of the drawn picture, and discrimination means 16, 17 discriminate the polarity of interpolation data obtained from the 2nd interpolation means 3, 15 and gives the result to a picture draw control means 18. In the means 18, whether or not a picture is to be drawn at each pixel as to the interpolation data from the 1st interpolation means 1, 5, 6, 7 based on the discrimination signal outputted from the discrimination means 16, 17 and the sectional view is drawn.
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