// Find the point of intersection between
// the lines p1 --> p2 and p3 --> p4.
public static PointF?FindIntersection(PointF p1, PointF p2, PointF p3, PointF p4)
{
// Get the segments' parameters.
float dx12 = p2.X - p1.X;
float dy12 = p2.Y - p1.Y;
float dx34 = p4.X - p3.X;
float dy34 = p4.Y - p3.Y;
// Solve for t1 and t2
float denominator = (dy12 * dx34 - dx12 * dy34);
float t1 = ((p1.X - p3.X) * dy34 + (p3.Y - p1.Y) * dx34) / denominator;
if (float.IsInfinity(t1))
{
// The lines are parallel (or close enough to it).
return(null);
}
float t2 = ((p3.X - p1.X) * dy12 + (p1.Y - p3.Y) * dx12) / -denominator;
// The segments intersect if t1 and t2 are between 0 and 1.
var segments_intersect =
((t1 >= 0) && (t1 <= 1) &&
(t2 >= 0) && (t2 <= 1));
// Find the point of intersection.
if (segments_intersect)
{
return(new PointF(p1.X + dx12 * t1, p1.Y + dy12 * t1));
}
return(null);
}
// Find the point of intersection between
// the lines p1 --> p2 and p3 --> p4.
// Находит пересечение отрезков, если точно известно, что они пересекаются
public static PointF Intersection(PointF p1, PointF p2, PointF p3, PointF p4)
{
// Get the segments' parameters.
float dx12 = p2.X - p1.X;
float dy12 = p2.Y - p1.Y;
float dx34 = p4.X - p3.X;
float dy34 = p4.Y - p3.Y;
// Solve for t1 and t2
float denominator = (dy12 * dx34 - dx12 * dy34);
float t1 = ((p1.X - p3.X) * dy34 + (p3.Y - p1.Y) * dx34) / denominator;
// Find the point of intersection.
return(new PointF(p1.X + dx12 * t1, p1.Y + dy12 * t1));
}
// Find the point of intersection between
// the lines p1 --> p2 and p3 --> p4.
public static void FindIntersection(
PointF p1, PointF p2, PointF p3, PointF p4,
out bool lines_intersect, out bool segments_intersect,
out PointF intersection,
out PointF close_p1, out PointF close_p2)
{
// Get the segments' parameters.
float dx12 = p2.X - p1.X;
float dy12 = p2.Y - p1.Y;
float dx34 = p4.X - p3.X;
float dy34 = p4.Y - p3.Y;
// Solve for t1 and t2
float denominator = (dy12 * dx34 - dx12 * dy34);
float t1 =
((p1.X - p3.X) * dy34 + (p3.Y - p1.Y) * dx34)
/ denominator;
if (float.IsInfinity(t1))
{
// The lines are parallel (or close enough to it).
lines_intersect = false;
segments_intersect = false;
intersection = new PointF(float.NaN, float.NaN);
close_p1 = new PointF(float.NaN, float.NaN);
close_p2 = new PointF(float.NaN, float.NaN);
return;
}
lines_intersect = true;
float t2 =
((p3.X - p1.X) * dy12 + (p1.Y - p3.Y) * dx12)
/ -denominator;
// Find the point of intersection.
intersection = new PointF(p1.X + dx12 * t1, p1.Y + dy12 * t1);
// The segments intersect if t1 and t2 are between 0 and 1.
segments_intersect =
((t1 >= 0) && (t1 <= 1) &&
(t2 >= 0) && (t2 <= 1));
// Find the closest points on the segments.
if (t1 < 0)
{
t1 = 0;
}
else if (t1 > 1)
{
t1 = 1;
}
if (t2 < 0)
{
t2 = 0;
}
else if (t2 > 1)
{
t2 = 1;
}
close_p1 = new PointF(p1.X + dx12 * t1, p1.Y + dy12 * t1);
close_p2 = new PointF(p3.X + dx34 * t2, p3.Y + dy34 * t2);
}
