public static Circle2d[] PointPoint(Point2d p1, Point2d p2, double radius)
{
// compute the circles which intersect at p1,p2 with radius 'rad'
double a = p1.Distance(p2);
if (MathUtil.IsZero(a))
{
return(null); //through one point
}
double d = 4.0 * radius * radius - a * a;
if (d < 0.0)
{
return(null); //not possible
}
d = Math.Sqrt(d) * 0.5;
//vector from midpoint of p1-p2 to center of circles
//that is vector p2-p1, rotaded 90 degrees, normalized and multiplied by distance to circle center
double vx = ((p2.Y - p1.Y) / a) * d;
double vy = -((p2.X - p1.X) / a) * d;
double midx = (p1.X + p2.X) * 0.5;
double midy = (p1.Y + p2.Y) * 0.5;
return(new Circle2d[] {
new Circle2d(midx + vx, midy + vy, radius),
new Circle2d(midx - vx, midy - vy, radius)
});
}
public override double Distance(Point2d p)
{
if (IsAngleOnArc(Center.Angle(p)))
{
return(Center.Distance(p) - Radius);
}
else
{
return(Math.Min(start.Distance(p), end.Distance(p)));
}
}
public static Parabola2d FromFocusAndDirectrix(Point2d focus, Line2d directrix)
{
Point2d ondir = directrix.ClosestPointInfinite(focus);
Point2d vertex = new Point2d(0.5 * (ondir.X + focus.X), 0.5 * (ondir.Y + focus.Y));
double focdist = focus.Distance(vertex);
double rot = focus.Angle(ondir) + MathUtil.Deg90;
if (focdist <= 1e-30)
{
return(null);
}
return(new Parabola2d(vertex, rot, focdist));
}
public override double Distance(Point2d p)
{
return(Math.Abs(center.Distance(p) - radius));
}
public static Circle2d From2Points(Point2d p1, Point2d p2)
{
Point2d center = new Point2d((p1.X + p2.X) / 2.0, (p1.Y + p2.Y) / 2.0);
return(new Circle2d(center, center.Distance(p1)));
}
