The document covers line clipping techniques in computer graphics, specifically the Cohen-Sutherland and Liang-Barsky algorithms. It explains the process of determining which parts of a line are visible within a defined clipping window using region codes and logical operations. The Nicholl-Lee-Nicholl algorithm is also mentioned as a method to optimize clipping by reducing the number of regions considered.

1. LINE CLIPPING
PRESENT BY
G.ALAMELU,MCA.,
EMGYADAVA WOMEN’S COLLEGE

2. What is line
clipping
 The line which is present outside the window Is to be
discarded and the line that is present inside the window
has to be accepted .

3. Cases in line
clipping

5. Cohen-
Sutherland
Line clipping
 B4 B3 B2 B1
 Left-b1=> 1 other will be 0
 Right –b2=> 1 other will be 0
 Bottom-b3=>1 other will be 0
 Top-b4=>1 other will be 0
 0000 => 4 Bit region
 Bit codes Called as Region code

6. Cases in
Cohen
 0000 => Completely interior (P1 & P2) => make visible
 P1 & P2 Both non zero => find logical AND=> output as
non zero
 =>completely exterior=>make invisible
 One of the point is non zero,logical AND is non zero =>
find intersect point.

7. Find intersect
in Cohen

8. Liang-barsky
Line clipping

9. NicholL lee
nicholl Line
clipping
 By creating more regions around clip window the NLN
algorithm avoids multiple clipping on an individual line
segment.
 Out of 9 regions Only 3 regions would be Considered.
 If p1 lies in any one of the other 6 region , we can move
it to One of the three Regions using symmetry
transformation .