public static bool IsRectangle(List <Vec2d> poly, double epsilon)
{
bool result = poly.Count == 4;
if (result)
{
// Check angles
for (int i = 0; result && i < poly.Count - 1; ++i)
{
int j = i + 1;
int k = (i + 2) % poly.Count;
Vec2d v1 = poly[j] - poly[i];
Vec2d v2 = poly[k] - poly[j];
v1.Normalize();
v2.Normalize();
double angle = Vec2d.AngleBetweenVectors(v1, v2);
while (angle < -Math.PI)
{
angle += 2.0 * Math.PI;
}
while (angle >= Math.PI)
{
angle -= 2.0 * Math.PI;
}
angle = Math.Abs(angle);
result = Math.Abs(angle - 0.5 * Math.PI) < epsilon;
}
}
return(result);
}