Ray-casting algorithm: Difference between revisions

the last "country" we land on is surely ''outside'' (since the inside of the polygon is finite, while the ray continues towards infinity). So, if we crossed an odd number of borders we waswere surely inside, otherwise we waswere outside; we can follow the ray backward to see it better: starting from outside, only an odd number of crossing can give an ''inside'': outside-inside, outside-inside-outside-inside, and so on (the - represents the crossing of a border).