Continuous zoning

a novel clipping thought

is put forward in this paper. The plane is divided into many different areas in different way continuously

which can abandon the lines outside the window easily and quickly

and avoid unnecessary computing the point of intersection. After secondary zoning

we implemented the series coding technique to save time and to establish connection between both codes. Then the point symmetry technique which is applied to multiple zoning is carried out in cubic zoning. The slope of the area boundary in cubic zoning is 0~

~45~ or infinity

which is suitable for the procedure realization. Comparing to secondary coding technique

point symmetry technique can avoid redundant operation of computing the point of intersection. The procedure realization clearly expresses that the algorithm in this paper can improve the line clipping efficiency.