Sutherland Hodgman polygon clipping algorithm is a very simple clipping algorithm to understand. I hope my slide will help you guys. -Thanks Tawfiq Ahmed

1.  Generally, any procedure, that identifies
that portion of a picture that are either
inside or outside of a specified region of
a space is referred as a clipping
algorithm or simply clipping.

2.  Clipping a polygon fill area needs more than line-clipping of
the polygon edges
-would produce and unconnected set of lines
 Must generate one or more closed polylines, which can be
filled with the assigned color or pattern

3.  Each edge of the polygon must be tested
against each edge of the clip rectangle;
new edges must be added, and existing
edges must be discarded, retained, or
divided. Multiple polygons may result
from clipping a single polygon. We need
an organized way to deal with all these
cases.

4.  Each edge goes through 4 clippers. The
rule for each edge for each clipper is:
 If first input vertex is outside, and
second is inside, output the
intersection and the second vertex
 If first both input vertices are inside,
then just output second vertex
 If first input vertex is inside, and
second is outside, output is the
intersection
 If both vertices are outside, output is
nothing

5. Polygons can be clipped against each
edge of the window one at a time.
Vertices which are kept after clipping
against one window edge are saved
for clipping against the remaining
edges.
Note that the number of vertices
usually changes and will often
increases.

8.  The Sutherland-Hodgman algorithm
correctly clips convex polygons, but
concave polygons may be displayed
with extraneous lines as
demonstrated in figure.

 Since there is only one output vertex
list, the last vertex in the list is
always joined to the first vertex.

9.  Complexity of this algorithm will increase if number of edges of polygon increase.
Algorithm has to calculate more number of intersection points over window
boundary.
 To overcome this problem we apply Weiler-Atherton Polygon Clipping Algorithm.