code: public Vector3d positiveZ(Vector3d dest) {
          dest.x = m10 * m21 - m11 * m20;
          dest.y = m20 * m01 - m21 * m00;
          dest.z = m00 * m11 - m01 * m10;
          return dest.normalize(dest);
      }
docs: /* (non-Javadoc)
  @see org.joml.Matrix4dc#positiveZ(org.joml.Vector3d)