168 471 Computer Graphics, KKU. Lecture 815 Parametric Line-Clipping Algorithm Introduced by Cyrud and Beck in 1978 Efficiently improved by Liang and Barsky Essentially find the parameter t from P(t) = P 0 + (P 1 -P 0 )t
168 471 Computer Graphics, KKU. Lecture 816 Parametric Line-Clipping Algorithm (cont.) Formally, intersections can be classified as PE (potentially entering) and PL (potentially leaving) on the basis of the angle between P 0 P 1 and N i Determine t E or t L for each intersection Select the line segment that has maximum t E and minimum t L If t E > t L, then trivially rejected
168 471 Computer Graphics, KKU. Lecture 819 Clipping Circles and Ellipses Firstly, do a trivial accept/reject test by intersecting the circle ’ s/elleipse ’ s extent with the clip rectengle. If intersection occurs, divide it into and do the trivial accept/reject test for each. If scan conversion is fast or if the circle is not too large, scissoring on a pixel-by-pixel basis would be more efficient.