https://tavianator.com/fast-branchless-raybounding-box-intersections-part-2-nans/

AABBRay.cs

    public bool Raycast(Ray r, out float distance)
    {
        Vector3 min = this.min;
        Vector3 max = this.max;

        float tmin = float.NegativeInfinity, tmax = float.PositiveInfinity;

        Vector3 dir_inv = new Vector3();
        dir_inv.x = r.direction.x == 0 ? float.PositiveInfinity : 1 / r.direction.x;
        dir_inv.y = r.direction.y == 0 ? float.PositiveInfinity : 1 / r.direction.y;
        dir_inv.z = r.direction.z == 0 ? float.PositiveInfinity : 1 / r.direction.z;

        distance = 0;

        for (int i = 0; i < 3; ++i)
        {
            float t1 = (min[i] - r.origin[i]) * dir_inv[i];
            float t2 = (max[i] - r.origin[i]) * dir_inv[i];

            tmin = Mathf.Max(tmin, Mathf.Min(t1, t2));
            tmax = Mathf.Min(tmax, Mathf.Max(t1, t2));

            distance = tmin * tmin;
        }
        distance = Mathf.Sqrt(distance);
        return tmax > Mathf.Max(tmin, 0.0f);
    }