Recently, virtual reality (VR) becomes more and more popular and provides users an immersive experience with a head-mounted display (HMD). However, in some applications, users have to interact with physical objects while immersed in VR. With a non-see-through HMD, it is difficult to perceive visual information from the real world. Users must recall the spatial layout of the real surroundings and grope around to find the physical objects. After locating the objects, it is still inconvenient to use them without any visual feedback, which would detract the immersive experience.