[MUSIC] In this video, we will compare two different VR display systems, the CAVE and HMD. In the previous video, we talked about the Oculus Rift, which is one of the most popular head mounted displays or HMD's currently on the market. We will spend lots of time on the technical features of HMD's later this week. But before then, I'd like to talk about a similar system that is less known to the public, the CAVE. The CAVE refers to a cave automatic virtual environment. It normally looks like this, just an empty room with at least four display walls. That's three walls around you, plus the floor. There are projectors behind the walls to project high resolution images. In order to perceive 3D stereo vision, the user would wear a pair of shutter glasses. So at any given time, they only see through one of their glasses. The displays are synced to the shutter glasses, so they will produce images that are for the correct eye at the correct moment. And this switches at least 60 times per second to produce the illusion of 3D stereo vision, similar to HMDs. In the CAVE, we also have user dynamic control of view point. This is achieved by attaching the head tracking device on top of the shutter glasses, and updating the display in realtime according to the viewpoint of the user. So although you can probably have more than one user standing in the space, each wearing a pair of shutter glasses, only one of them could be wearing the head tracking device that is synced to the machine that renders the graphics. This will be the only person who has the dynamic control of view point. For other users, the display could feel a bit distorted. Finally, because of the four surrounding walls, the user feels that they are surrounded by the computer generated images rather than the real world. Again, all three features contribute to the immersive VR experience. In summary, the CAVE is designed to be used by a single user whose head position will be tracked. It takes a large and dedicated space. It's normally set up as a fixture in research labs in both academia and industry. And truly, you can't carry your CAVE system with you. Because of the size of the display, you could have very high resolution, but you will need powerful machines to drive that. Both CAVEs and HMDs are designed for single users. You can have VR applications with multiple users, but each one will need their own display device, that is, either a CAVE or HMD. The CAVEs have a big screen with high resolution. In comparison, the HMD is currently much lower in their resolutions. The CAVEs take a large and dedicated space, while the HMDs are more flexible in their space requirements. [MUSIC]