public static bool LineIntersectsWithEllipse(Point2 a, Point2 b, Rect2 rect, bool onlySegment, out IList <Point2>?points)
{
if ((rect.Width == 0) || (rect.Height == 0) || ((a.X == b.X) && (a.Y == b.Y)))
{
points = null;
return(false);
}
if (rect.Width < 0)
{
throw new ArgumentException("Rectangle Width must be positive value.");
}
if (rect.Height < 0)
{
throw new ArgumentException("Rectangle Height must be positive value.");
}
double cx = rect.Left + (rect.Width / 2.0);
double cy = rect.Top + (rect.Height / 2.0);
double p1X = a.X - cx;
double p1Y = a.Y - cy;
double p2X = b.X - cx;
double p2Y = b.Y - cy;
double rx = rect.Width / 2.0;
double ry = rect.Height / 2.0;
double A = ((p2X - p1X) * (p2X - p1X) / rx / rx) + ((p2Y - p1Y) * (p2Y - p1Y) / ry / ry);
double B = (2 * p1X * (p2X - p1X) / rx / rx) + (2 * p1Y * (p2Y - p1Y) / ry / ry);
double C = (p1X * p1X / rx / rx) + (p1Y * p1Y / ry / ry) - 1;
var solutions = new List <double>();
double discriminant = (B * B) - (4 * A * C);
if (discriminant == 0)
{
solutions.Add(-B / 2 / A);
}
else if (discriminant > 0)
{
solutions.Add((-B + (double)Math.Sqrt(discriminant)) / 2 / A);
solutions.Add((-B - (double)Math.Sqrt(discriminant)) / 2 / A);
}
var result = new List <Point2>();
foreach (var t in solutions)
{
if (!onlySegment || ((t >= 0f) && (t <= 1f)))
{
double x = p1X + ((p2X - p1X) * t) + cx;
double y = p1Y + ((p2Y - p1Y) * t) + cy;
result.Add(new Point2(x, y));
}
}
if (result.Count > 0)
{
points = result;
return(true);
}
else
{
points = null;
return(false);
}
}
public static bool LineIntersectsWithRect(Point2 a, Point2 b, Rect2 rect, out double x0clip, out double y0clip, out double x1clip, out double y1clip)
{
double left = rect.Left;
double right = rect.Right;
double bottom = rect.Bottom;
double top = rect.Top;
double x0 = a.X;
double y0 = a.Y;
double x1 = b.X;
double y1 = b.Y;
double t0 = 0.0;
double t1 = 1.0;
double dx = x1 - x0;
double dy = y1 - y0;
double p = 0.0, q = 0.0, r;
x0clip = 0.0;
y0clip = 0.0;
x1clip = 0.0;
y1clip = 0.0;
for (int edge = 0; edge < 4; edge++)
{
if (edge == 0)
{
p = -dx;
q = -(left - x0);
}
if (edge == 1)
{
p = dx;
q = right - x0;
}
if (edge == 2)
{
p = dy;
q = bottom - y0;
}
if (edge == 3)
{
p = -dy;
q = -(top - y0);
}
r = q / p;
if (p == 0.0 && q < 0.0)
{
return(false);
}
if (p < 0.0)
{
if (r > t1)
{
return(false);
}
else if (r > t0)
{
t0 = r;
}
}
else if (p > 0.0)
{
if (r < t0)
{
return(false);
}
else if (r < t1)
{
t1 = r;
}
}
}
x0clip = x0 + (t0 * dx);
y0clip = y0 + (t0 * dy);
x1clip = x0 + (t1 * dx);
y1clip = y0 + (t1 * dy);
return(true);
}
