Problem:

For each pixel determine if it is inside or outside of a given polygon.

Approach:

• from the point being tested cast a ray in an arbitary direction
• if the number of crossings is odd then the point is inside
• if the number of crossings is even then the point is outside

• Very fragile algorithm
• What if ray crosses a vertex?
• What if ray falls on an edge?
• Commonly used in ECAD
• Suitable for H/W