How to determine which side of a polygon edge is inside a polygon, and which is outside?

Question

I have an edge of a polygon (convex or concave). I want to find out if, going straight from start to end point of that edge, I have to turn right or left to get inside or ou

Answer 1

Traverse the whole polygon in that direction. If you find that you went clockwise, then the interior is to the right; if you went counter-clockwise, it's to the left.