public static bool CircleToCircle(Circle a, Circle b)
{
double c2 = (a.cX - b.cX) * (a.cX - b.cX) + (a.cY - b.cY) * (a.cY - b.cY);
double r2 = (a.R + b.R) * (a.R + b.R);
return c2 <= r2;
}
public static bool CircleToRectangle(Circle a, Rectangle b)
{
//double cdX = Math.Abs(a.X - b.X - b.W/2);
//double cdY = Math.Abs(a.Y - b.Y - b.H/2);
//if (cdX > (b.W/2 + a.R))
//{
// return false;
//}
//if (cdY > (b.H/2 + a.R))
//{
// return false;
//}
//if (cdX <= (b.W/2))
//{
// return true;
//}
//if (cdY > (b.H/2))
//{
// return true;
//}
//double cornerDistance_sq = ((cdX - b.W/2)*(cdX - b.W/2)) +
// ((cdY - b.H/2)*(cdY - b.H/2));
//return (cornerDistance_sq <= (a.R*a.R));
double dmin = 0;
double[] C = new[] { a.cX, a.cY };
double[] Bmin = new[] { b.X, b.Y };
double[] Bmax = new[] { b.X + b.W, b.Y + b.H };
for (int i = 0; i < C.Length; i++)
{
if (C[i] < Bmin[i]) dmin += (C[i] - Bmin[i]) * (C[i] - Bmin[i]);
else if (C[i] > Bmax[i]) dmin += (C[i] - Bmax[i]) * (C[i] - Bmax[i]);
}
return dmin <= a.R * a.R;
}
