# Real-Time 3D Reconstruction Method for Holographic Telepresence
## 3 Proposed Real-Time 3D Reconstruction for Holographic Telepresence  
After the real-time 3D reconstruction phase has been done, the next step is to enable the 3D telepresence. The textured 3D model of the local user produced was then transferred to a remote location through the network to be displayed at a remote location in real-time to enable the local and remote user to engage with one another through the telepresence. The overall framework of the proposed real-time 3D reconstruction for a 3D holographic telepresence is shown in Figure 4.  
Figure 4: The framework of real-time 3D reconstruction for holographic telepresence.  
The textured 3D model, along with the audio of the local user, is then transmitted over the network to the remote location, as in Figure 5. These data will first be encoded to be compressed according to the suitable bandwidth of data transmission through an internet protocol. After the data was sent and received at the remote location, the data was decompressed using a lossless compression method on the remote client laptop and ready to be displayed in the reconstructed textured 3D model of the local user. The lossless compression method used for this research is the Lempel-Ziv-Free (LZF) compression, as recommended by [PERSON] et al. [31]. This compression algorithm requires a minimal code space and working memory. The mesh data with audio input of remote users was also sent over to the local location through the network.  
Once the data sent from the local site were received on the remote site, the mesh data was rendered and displayed using holographic projection. As illustrated in Figure 6, Z-Hologram was chosen as the display device to project the virtual reconstructed local user onto a real-world environment for remote users to experience and interact with it.  
For Z-Hologram, the effect of floating virtual 3D images for the viewers is formed when the reference beam and the object or image source beam are incident on opposite sides of the reflective transparent surface, as illustrated in Figure 7. The beams interfere and record an image called a holographic image. To reconstruct the image, a point source of white light illuminates the hologram from the proper angle, and the viewer looks at it from the same side as the light source.  
Figure 5: The data transmission over the network for the telepresence system.  
Figure 6: The Z-Hologram setup structure.  
As agreed with by [PERSON] and [PERSON] [32], the hologram technique can enhance the realism and the immersion to provide the realizable 3D stereoscopic vision when the floating hologram projecting the 2D image to represent the 3D image in the air uses the glass panel. [PERSON] et al. [33] also claimed that, using the Pepper's Ghost principle, a 2D image satisfying certain psychological depth cues such as occlusion can be displayed, thereby providing the viewers with 3D feelings. Thus, the 3D data that has been generated and displayed using the Z-hologram can be perceived by the user in 3D and helps provide a more absorbing experience of viewing the 3D data for the user. Using Z-hologram can benefit from 3D data as it able to provide the viewer with 3D impressions without the use of wearable hardware. Besides, a VR headset does not support a holographic display because any object inside VR is considered as a virtual object. Holographic projection is when the object is projected onto the real-world. This article also mentions that the use of hardware can restrict user movement and cause discomfort to the user.