/// <summary>
/// True if this crosses the line and returns the intersectin points.
/// </summary>
/// <param name="Line">The line.</param>
/// <param name="IntersectionPts">The point set to recieve the result.</param>
public bool Crosses(C2DLine Line, List <C2DPoint> IntersectionPts)
{
double x1 = Line.point.x;
double x2 = Line.point.x + Line.vector.i;
double x3 = _Centre.x;
double y1 = Line.point.y;
double y2 = Line.point.y + Line.vector.j;
double y3 = _Centre.y;
double r = Radius;
double a = (x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1);
double b = 2 * ((x2 - x1) * (x1 - x3) + (y2 - y1) * (y1 - y3));
double c = x3 * x3 + y3 * y3 + x1 * x1 + y1 * y1 - 2 * (x3 * x1 + y3 * y1) - r * r;
double u = -b / (2 * a);
C2DPoint ptClosestToCen = new C2DPoint();
if (u < 0)
{
ptClosestToCen.Set(Line.point);
}
else if (u > 1)
{
ptClosestToCen.Set(Line.GetPointTo());
}
else
{
C2DVector V1 = new C2DVector(Line.vector);
V1.Multiply(u);
ptClosestToCen = Line.point.GetPointTo(V1);
}
double dDist = ptClosestToCen.Distance(_Centre);
if (dDist > Radius)
{
return(false);
}
else
{
// Calculate the points.
double d1 = b * b - 4 * a * c;
Debug.Assert(d1 >= 0);
if (d1 < 0)
{
return(false);
}
else if (d1 == 0)
{
double p1 = -b / (2 * a);
IntersectionPts.Add(Line.GetPointOn(p1));
return(true);
}
else
{
d1 = Math.Sqrt(d1);
double p1 = (-b + d1) / (2 * a);
double p2 = (-b - d1) / (2 * a);
bool bResult = false;
if (p2 >= 0 && p2 <= 1)
{
bResult = true;
IntersectionPts.Add(Line.GetPointOn(p2));
}
if (p1 >= 0 && p1 <= 1)
{
bResult = true;
IntersectionPts.Add(Line.GetPointOn(p1));
}
return(bResult);
}
}
}
/// <summary>
/// True if this crosses the line and returns the intersectin points.
/// </summary>
/// <param name="Line">The line.</param>
/// <param name="IntersectionPts">The point set to recieve the result.</param>
public bool Crosses(C2DLine Line, List<C2DPoint> IntersectionPts)
{
double x1 = Line.point.x;
double x2 = Line.point.x + Line.vector.i;
double x3 = _Centre.x;
double y1 = Line.point.y;
double y2 = Line.point.y + Line.vector.j;
double y3 = _Centre.y;
double r = Radius;
double a = (x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1);
double b = 2 * ((x2 - x1) * (x1 - x3) + (y2 - y1) * (y1 - y3));
double c = x3 * x3 + y3 * y3 + x1 * x1 + y1 * y1 - 2 * (x3 * x1 + y3 * y1) - r * r;
double u = -b / (2 * a);
C2DPoint ptClosestToCen = new C2DPoint();
if (u < 0)
{
ptClosestToCen.Set( Line.point );
}
else if (u > 1)
{
ptClosestToCen.Set( Line.GetPointTo());
}
else
{
C2DVector V1 = new C2DVector(Line.vector);
V1.Multiply(u);
ptClosestToCen = Line.point.GetPointTo(V1);
}
double dDist = ptClosestToCen.Distance(_Centre);
if (dDist > Radius)
{
return false;
}
else
{
// Calculate the points.
double d1 = b * b - 4 * a * c;
Debug.Assert(d1 >= 0);
if (d1 < 0)
return false;
else if (d1 == 0)
{
double p1 = -b / (2 * a);
IntersectionPts.Add(Line.GetPointOn(p1));
return true;
}
else
{
d1 = Math.Sqrt(d1);
double p1 = (-b + d1) / (2 * a);
double p2 = (-b - d1) / (2 * a);
bool bResult = false;
if (p2 >= 0 && p2 <= 1)
{
bResult = true;
IntersectionPts.Add(Line.GetPointOn(p2));
}
if (p1 >= 0 && p1 <= 1)
{
bResult = true;
IntersectionPts.Add(Line.GetPointOn(p1));
}
return bResult;
}
}
}
