- Need an area primitive
- Simple polygon:
- Planar set of ordered points,
(sometimes we repeat at end of list)

- No holes
- No line crossing

\

- Planar set of ordered points,
- Normally define an interior and exterior
Points ordered in counter-clockwise order

To the ``left'' as we traverse is inside

\

- Try to avoid degeneracies, but sometimes unavoidable
\

- We prefer
*Convex*polygons to*Concave*polygons\

Polygon is convex if for any two points inside polygon, the line segment joining these two points is also inside.

Convex polygons ``behave'' better when shading, etc

- Although convex polygons normally ``well behaved'' under
affine transformation, affine transformations may
introduce degeneracies
Example: Orthographic projection may project entire polygon to a line segment.

CS488/688: Introduction to Interactive Computer Graphics

University of Waterloo

Computer Graphics Lab