code: protected double intersectionX (IRay3 ray, double x) {
          IVector3 origin = ray.origin(), dir = ray.direction();
          double t = (x - origin.x()) / dir.x();
          if (t < 0f) {
              return Float.MAX_VALUE;
          }
          double iy = origin.y() + t*dir.y(), iz = origin.z() + t*dir.z();
          return (iy >= _minExtent.y && iy <= _maxExtent.y &&
              iz >= _minExtent.z && iz <= _maxExtent.z) ? t : Float.MAX_VALUE;
      }
docs: Helper method for {@link #intersection}. Finds the <code>t</code> value where the ray
  intersects the box at the plane where x equals the value specified, or returns
  {@link Float#MAX_VALUE} if there is no such intersection.