public static Point[] LineCircleIntersection(LineGeometry line, CircleGeometry circle)
{
if (line == null || circle == null)
{
return(new Point[0]);
}
if (!line.Bounds.IntersectsWith(circle.Bounds))
{
return(new Point[0]);
}
Vector d = line.EndPoint - line.StartPoint;
Vector f = line.StartPoint - circle.Center;
double a = d * d;
double b = 2 * f * d;
double c = (f * f) - (circle.Radius * circle.Radius);
double discriminant = (b * b) - (4 * a * c);
if (discriminant < 0)
{
return(new Point[0]);
}
discriminant = Math.Sqrt(discriminant);
double t1 = (-b - discriminant) / (2 * a);
double t2 = (-b + discriminant) / (2 * a);
Point p1 = line.StartPoint + Vector.Multiply(d, t1);
Point p2 = line.StartPoint + Vector.Multiply(d, t2);
if (IsPointOnLineSegment(p1, line) && IsPointOnLineSegment(p2, line))
{
return new[] { p1, p2 }
}
;
if (IsPointOnLineSegment(p1, line))
{
return new[] { p1 }
}
;
if (IsPointOnLineSegment(p2, line))
{
return new[] { p2 }
}
;
return(new Point[0]);
}
public static Point[] CircleCircleIntersection(CircleGeometry firstCircle, CircleGeometry secondCircle)
{
if (firstCircle == null || secondCircle == null)
{
return(new Point[0]);
}
double cx0 = firstCircle.Center.X;
double cx1 = secondCircle.Center.X;
double cy0 = firstCircle.Center.Y;
double cy1 = secondCircle.Center.Y;
double radius0 = firstCircle.Radius;
double radius1 = secondCircle.Radius;
double dx = cx0 - cx1;
double dy = cy0 - cy1;
double dist = Math.Sqrt((dx * dx) + (dy * dy));
if (dist > radius0 + radius1)
{
return(new Point[0]);
}
if (dist < Math.Abs(radius0 - radius1))
{
return(new Point[0]);
}
if ((dist.AlmostEquals(0d)) && (radius0.AlmostEquals(radius1)))
{
return(new Point[0]);
}
double a = ((radius0 * radius0) - (radius1 * radius1) + (dist * dist)) / (2 * dist);
double h = Math.Sqrt((radius0 * radius0) - (a * a));
double cx2 = cx0 + (a * (cx1 - cx0) / dist);
double cy2 = cy0 + (a * (cy1 - cy0) / dist);
return(new []
{
new Point(
cx2 + (h * (cy1 - cy0) / dist),
cy2 - (h * (cx1 - cx0) / dist)),
new Point(
cx2 - (h * (cy1 - cy0) / dist),
cy2 + (h * (cx1 - cx0) / dist))
});
}
