//The list describing the polygon has to be sorted either clockwise or counter-clockwise because we have to identify its edges
public static bool ContainsPoint(List <Vector2> polygonPoints, Vector2 point)
{
//Step 1. Find a point outside of the polygon
//Pick a point with a x position larger than the polygons max x position, which is always outside
Vector2 maxXPosVertex = polygonPoints[0];
for (int i = 1; i < polygonPoints.Count; i++)
{
if (polygonPoints[i].x > maxXPosVertex.x)
{
maxXPosVertex = polygonPoints[i];
}
}
//The point should be outside so just pick a number to make it outside
Vector2 pointOutside = maxXPosVertex + new Vector2(10f, 0f);
//Step 2. Create an edge between the point we want to test with the point thats outside
Vector2 l1_p1 = point;
Vector2 l1_p2 = pointOutside;
//Step 3. Find out how many edges of the polygon this edge is intersecting
int numberOfIntersections = 0;
for (int i = 0; i < polygonPoints.Count; i++)
{
//Line 2
Vector2 l2_p1 = polygonPoints[i];
int iPlusOne = ClampListIndex(i + 1, polygonPoints.Count);
Vector2 l2_p2 = polygonPoints[iPlusOne];
//Are the lines intersecting?
if (Lines.AreLinesIntersecting(l1_p1, l1_p2, l2_p1, l2_p2, true))
{
numberOfIntersections += 1;
}
}
//Step 4. Is the point inside or outside?
bool isInside = true;
//The point is outside the polygon if number of intersections is even or 0
if (numberOfIntersections == 0 || numberOfIntersections % 2 == 0)
{
isInside = false;
}
return(isInside);
}
