HandModel.GetPalmNormal C# (CSharp) Method

  public Vector3 GetPalmNormal() {
    if (controller_ != null && hand_ != null) {
      return controller_.transform.TransformDirection(hand_.PalmNormal.ToUnity(mirror_z_axis_));
    }
    if (palm) {
      return -palm.up;
    }
    return -Vector3.up;
  }

    void updateLeftHandFacingUp()
    {
        Vector3 upCam      = mainCamera.transform.up;
        float   difference = Vector3.Angle(leftHandModel.GetPalmNormal(), upCam);

        leftHandFacingUp = difference < MAX_ANGLE_DIFFERENCE_FOR_INTERFACE && leftHand.activeSelf;
    }