private static double incidenceLineCircle(NPoint point1, NPoint point2, double radius)
{
double determinant = point1.CrossProduct(point2);
double lineLength = Algebra.SRSS((point2.X - point1.X), (point2.Y - point1.Y));
return(incidenceLineCircle(radius, lineLength, determinant));
}
/// <summary>
/// The y-coordinates of a line intersecting a circle centered at 0,0.
/// </summary>
/// <param name="point1">First point forming the line.</param>
/// <param name="point2">Second point forming the line.</param>
/// <param name="radius">Radius of the circle centered at 0,0.</param>
public static double[] CircleLineIntersectY(NPoint point1, NPoint point2, double radius)
{
Offset delta = new Offset(point1, point2);
double determinant = point1.CrossProduct(point2);
double lineLength = Algebra.SRSS(delta.X(), delta.Y());
double incidence = incidenceLineCircle(radius, lineLength, determinant);
return(CircleLineIntersectY(radius, lineLength, incidence, determinant, delta));
}
/// <summary>
///
/// </summary>
/// <param name="point1"></param>
/// <param name="point2"></param>
/// <param name="radius"></param>
/// <returns></returns>
public static NPoint[] CircleLineIntersect(NPoint point1, NPoint point2, double radius)
{
Offset delta = new Offset(point1, point2);
double determinant = point1.CrossProduct(point2);
double lineLength = Algebra.SRSS(delta.X(), delta.Y());
double incidence = incidenceLineCircle(radius, lineLength, determinant);
double[] xCoords = CircleLineIntersectX(radius, lineLength, incidence, determinant, delta);
double[] yCoords = CircleLineIntersectY(radius, lineLength, incidence, determinant, delta);
return(new[]
{
new NPoint(xCoords[0], yCoords[0]),
new NPoint(xCoords[1], yCoords[1])
});
}