Abstract: The result of clipping is discussed according to possible positions for both endpoints of a line segment in relation to circular window. The intersection is determined by comparing the slope of the tangent with the slope of the line segment and the ingenious region detection about the point when both endpoints of the line segment are outside of the circular window. Simplify the intersection equation by means of the intersection calculation with the parametric form when the intersection actually happens. The experimental results show that the new algorithm further improves the clipping efficiency.

Key words: computer application, line clipping against circular window, slope comparison, region detection