//test if circle collides with other circle
//used in robot collision detection
public bool Collide(Circle2D other)
{
var dx = other.p.x - p.x;
var dy = other.p.y - p.y;
dx *= dx;
dy *= dy;
var radSum = other.Radius + Radius;
radSum *= radSum;
return (dx + dy) < radSum;
}
//calculate the nearest intersection of this line
//with a circle -- if the line is interpreted as a ray
//going from its first endpoint to the second
public double nearest_intersection(Circle2D C, out bool found)
{
var dx = P2.x - P1.x;
var dy = P2.y - P1.y;
var px = P1.x - C.p.x;
var py = P1.y - C.p.y;
var a = dx*dx + dy*dy;
var b = 2*px*dx + 2*py*dy;
var c = px*px + py*py - C.Radius*C.Radius;
var det = b*b - 4.0*a*c;
if (det < 0.0)
{
found = false;
return -1.0;
}
var sqrtDet = Math.Sqrt(det);
var t1 = (-b + sqrtDet)/(2*a);
var t2 = (-b - sqrtDet)/(2*a);
found = false;
var t = 0.0;
if (t2 < 0)
{
if (t1 > 0)
{
found = true;
t = t1;
}
}
else
{
found = true;
t = t2;
}
if (!found)
return -1.0;
return t*Math.Sqrt(dx*dx + dy*dy);
}
public Circle2D(Circle2D other)
{
p = other.p;
Radius = other.Radius;
}
