public static bool PointInPolygon(Polygon2 poly, Vector2 point)
{
var ls = new LineSegment2() { A = point, B = new Vector2() { X = poly.BoundingBox.Item1.X, Y = point.Y } };
var iCount = (from x in poly.Segments where LineSegment2.Intersection(ls, x) != null select x).Count() % 2;
return iCount > 0;
}
public static Vector2 Intersection(LineSegment2 L1, LineSegment2 L2)
{
var a = Math.Min(L1.A.X, L1.B.X);
var b = Math.Max(L1.A.X, L1.B.X);
var c = Math.Min(L2.A.X, L2.B.X);
var d = Math.Max(L2.A.X, L2.B.X);
if (c - b >= 0)
return null;
if ((b - a) == 0 && (d - c) == 0)
return null;
if ((b - a) == 0)
{
var s2 = L2.Slope;
var b2 = L2.Base;
double ty = s2 * b + b2;
var miny = Math.Min(L1.A.Y, L1.B.Y);
var maxy = Math.Max(L1.A.Y, L1.B.Y);
if (miny <= ty && ty <= maxy) return new Vector2(){X=b, Y=ty};
return null;
}
if ((d - c) == 0)
{
var s1 = L1.Slope;
var b1 = L1.Base;
double ty = s1 * d + b1;
var miny = Math.Min(L2.A.Y, L2.B.Y);
var maxy = Math.Max(L2.A.Y, L2.B.Y);
if (miny <= ty && ty <= maxy) return new Vector2() { X = d, Y = ty };
return null;
}
var slope1 = L1.Slope;
var slope2 = L2.Slope;
var base1 = L1.Base;
var base2 = L2.Base;
if (slope1 == slope2 && base1 != base2)
return null;
var xTest = (base2 - base1) / (slope1 - slope2);
var yTest = slope1 * xTest + base1;
var xMin = Math.Min(b, c);
var xMax = Math.Max(b, c);
if (xMin <= xTest && xTest <= xMax) return new Vector2() { X = xTest, Y = yTest };
return null;
}
public static double AcuteIntersectionAngle(LineSegment2 L1, LineSegment2 L2)
{
return Math.Atan((L2.Slope - L1.Slope) / (1 + (L2.Slope * L1.Slope)));
}
public static Vector2 ReflectionUnitVector(LineSegment2 L1, LineSegment2 L2)
{
var angle = ReflectionAngle(L1, L2);
return new Vector2() { X = Math.Sin(angle), Y = Math.Cos(angle) };
}
public static double ReflectionAngle(LineSegment2 L1, LineSegment2 L2)
{
return L2.Angle + AcuteIntersectionAngle(L1, L2);
}
public static double ObtuseIntersectionAngle(LineSegment2 L1, LineSegment2 L2)
{
return Math.PI - AcuteIntersectionAngle(L1, L2);
}
