public ConvexPolygon2D GetIntersectionOfPolygons(ConvexPolygon2D poly1, ConvexPolygon2D poly2)
{
List <Point2D> clippedCorners = new List <Point2D>();
//Add the corners of poly1 which are inside poly2
for (int i = 0; i < poly1.Corners.Length; i++)
{
if (IsPointInsidePoly(poly1.Corners[i], poly2))
{
AddPoints(clippedCorners, new Point2D[] { poly1.Corners[i] });
}
}
//Add the corners of poly2 which are inside poly1
for (int i = 0; i < poly2.Corners.Length; i++)
{
if (IsPointInsidePoly(poly2.Corners[i], poly1))
{
AddPoints(clippedCorners, new Point2D[] { poly2.Corners[i] });
}
}
//Add the intersection points
for (int i = 0, next = 1; i < poly1.Corners.Length; i++, next = (i + 1 == poly1.Corners.Length) ? 0 : i + 1)
{
AddPoints(clippedCorners, GetIntersectionPoints(poly1.Corners[i], poly1.Corners[next], poly2));
}
return(new ConvexPolygon2D(OrderClockwise(clippedCorners.ToArray())));
}
// taken from https://wrf.ecse.rpi.edu//Research/Short_Notes/pnpoly.html
public bool IsPointInsidePoly(Point2D test, ConvexPolygon2D poly)
{
int i;
int j;
bool result = false;
for (i = 0, j = poly.Corners.Length - 1; i < poly.Corners.Length; j = i++)
{
if ((poly.Corners[i].Y > test.Y) != (poly.Corners[j].Y > test.Y) &&
(test.X < (poly.Corners[j].X - poly.Corners[i].X) * (test.Y - poly.Corners[i].Y) / (poly.Corners[j].Y - poly.Corners[i].Y) + poly.Corners[i].X))
{
result = !result;
}
}
return(result);
}
public virtual Point2D[] GetIntersectionPoints(Point2D l1p1, Point2D l1p2, ConvexPolygon2D poly)
{
List <Point2D> intersectionPoints = new List <Point2D>();
for (int i = 0; i < poly.Corners.Length; i++)
{
int next = (i + 1 == poly.Corners.Length) ? 0 : i + 1;
Point2D ip = GetIntersectionPoint(l1p1, l1p2, poly.Corners[i], poly.Corners[next]);
if (ip != null)
{
intersectionPoints.Add(ip);
}
}
return(intersectionPoints.ToArray());
}
