Lecture Computer graphics: Lecture 21 - Fasih ur Rehman

This chapter explain why computer literacy is vital to success in today''s world, describe the five components of a computer, discuss the advantages and disadvantages that users experience when working with computers, discuss the uses of the Internet and World Wide Web,...

Computer Graphics

Lecture 21 Fasih ur Rehman

Last Class

• Clipping Algorithms

Today’s Agenda

• Clipping Algorithms

Cohen – Sutherland Line

Clipping

Cohen – Sutherland Line

Clipping

• The view window is divided into regions as shown in the figure

• Each region is assigned a 4-bit outcode

Cohen – Sutherland Line

Clipping

• Most significant bit (MSB) called bit 1 indicates y-value of points are above ymax

• Bit 2 indicates y-value of points are below ymin

• Bit 3 indicates x-value of points are to the right of Xmax

• Bit 4 indicates x-value of points are to the left of Xmin

Cohen – Sutherland Line

Clipping

• For each line segment

operation)

• trivial accept (Line AB of the Figure)

– Else

• AND (bitwise) vertex outcodes

• if result 0, trivial reject (e g EF)

Cohen – Sutherland Line

Clipping

• If line cannot be trivially accepted or

rejected, subdivide the line into the

segments either or both of which can be

rejected

intersects

(outside the view window) and assign new

outcode to new vertex

Cohen – Sutherland Line

Clipping

rejected, subdivide the line so that o both or either

of the two segments can be discarded

To find intersection point

Parametric Form of Line

• Clipping

• Fundamentals of Computer Graphics Third Edition by Peter Shirley and Steve

Marschner

• Interactive Computer Graphics, A

Top-down Approach with OpenGL (Sixth

Edition) by Edward Angel