public static void ClosestSegmentToSegments(Segment2f seg0, Segment2f seg1, out float s, out float t)
{
Vector2f ab0 = seg0.B - seg0.A;
Vector2f ab1 = seg1.B - seg1.A;
Vector2f a01 = seg0.A - seg1.A;
float d00 = Vector2f.Dot(ab0, ab0);
float d11 = Vector2f.Dot(ab1, ab1);
float d1 = Vector2f.Dot(ab1, a01);
s = 0;
t = 0;
//Check if either or both segments degenerate into points.
if (d00 < FMath.EPS && d11 < FMath.EPS)
{
return;
}
if (d00 < FMath.EPS)
{
//First segment degenerates into a point.
s = 0;
t = FMath.Clamp01(d1 / d11);
}
else
{
float c = Vector2f.Dot(ab0, a01);
if (d11 < FMath.EPS)
{
//Second segment degenerates into a point.
s = FMath.Clamp01(-c / d00);
t = 0;
}
else
{
//The generate non degenerate case starts here.
float d2 = Vector2f.Dot(ab0, ab1);
float denom = d00 * d11 - d2 * d2;
//if segments not parallel compute closest point and clamp to segment.
if (!FMath.IsZero(denom))
{
s = FMath.Clamp01((d2 * d1 - c * d11) / denom);
}
else
{
s = 0;
}
t = (d2 * s + d1) / d11;
if (t < 0.0f)
{
t = 0.0f;
s = FMath.Clamp01(-c / d00);
}
else if (t > 1.0f)
{
t = 1.0f;
s = FMath.Clamp01((d2 - c) / d00);
}
}
}
}
