Create Quaternion from two unit vectors for rotation

CreateFromUnitVector.cs

using System.Numerics;

static class Rotation
{
    private static Quaternion CreateFromUnitVectors(Vector3 from, Vector3 to)
    {
        Vector3 v1;
        var r = Vector3.Dot(from, to) + 1;
        if (r < 0.000001f)
        {
            r = 0;
            if (Math.Abs(from.X) > Math.Abs(to.X))
            {
                v1 = new Vector3(-from.Y, from.X, 0);
            }
            else
            {
                v1 = new Vector3(0, -from.Z, from.Z);
            }
        }
        else
        {
            v1 = Vector3.Cross(from, to);
        }

        var q = new Quaternion(v1, r);
        return Quaternion.Normalize(q);
    }
}

Code from Three.js (https://github.com/mrdoob/three.js/blob/master/src/math/Quaternion.js)