public static bool Intersection(Vector2 aStart, Vector2 aEnd, Vector2 bStart, Vector2 bEnd, out Vector2 intersection)
{
Vector2 aSize = aEnd - aStart, bSize = bEnd - bStart;
var cross = aSize.X * bSize.Y - aSize.Y * bSize.X;
// ReSharper disable once CompareOfFloatsByEqualityOperator
if (cross == 0f)
{
intersection = default;
return(false);
}
var crossReciprocal = 1.0f / cross;
var distStart = bStart - aStart;
var negDistStartY = -distStart.Y;
var checkA = MathF.FusedMultiplyAdd(distStart.X, aSize.Y, negDistStartY * aSize.X) * crossReciprocal;
var checkB = MathF.FusedMultiplyAdd(distStart.X, bSize.Y, negDistStartY * bSize.X) * crossReciprocal;
if (checkA < 0 || checkB < 0 || checkA > 1 || checkB > 1)
{
intersection = default;
return(false);
}
intersection = new Vector2(
MathF.FusedMultiplyAdd(checkB, aSize.X, aStart.X),
MathF.FusedMultiplyAdd(checkB, aSize.Y, aStart.Y)
);
return(true);
}
public static bool ContainsPoint(this ReadOnlySpan <Vector2> poly, Vector2 point)
{
var result = false;
var j = poly.Length - 1;
var pY = point.Y;
var pX = point.X;
for (var i = 0; i < poly.Length; i++)
{
var iY = poly[i].Y;
var jY = poly[j].Y;
var iX = poly[i].X;
var jX = poly[j].X;
if (iY < pY && jY >= pY ||
jY < pY && iY >= pY &&
MathF.FusedMultiplyAdd(
(pY - iY) / (jY - iY),
jX - iX,
iX
) < pX)
{
result = !result;
}
j = i;
}
return(result);
}
