Holography (Earth-5875)

Holography is a technological system able to form a visual representation of a destined object in three dimensions. Holography is used by advanced sapient species in the galaxy, such as humans and the ex-Covenant species, for numerous functions, such as communication, sensory display, and decoys. Apparel used to project holograms are known as holotanks.

Human
The UNSC employs holographic technology in numerous ways and fields, such as the communication between individual humans; a starship's captain "appear" on another vessel to deliver messages when access between two ships is impossible. Most UNSC ships, bases, and facilities have featured holotanks, which are used to project three dimensional topographical maps, either for study or military purposes.

Holography is also deeply present in civilian life, being heavily featured in computer terminals that can answer to physical inputs despite not being physical themselves. Nightclubs, such as Club Errera, employ holograms for numerous ends. Humans also use holograms in the form of holo-stills, holographic photographs.

Covenant
The Covenant's holographic technology was heavily based upon that of the forerunners. It was very superior to the technology used by the humanity, but still very inferior to its source material. The Covenant used holography to visually display space and ground for scientific and tactical reasons, allowing them to coordinate military attacks at higher precision. They also used holograms as decoys through holo-drones, which are able to cause physical harm to others and give the illusion of reality.

Other Covenant holograms, such as the ones used by the Hierarchs, were able to physically interact with their environment, in order to give sermons and speeches to the members of the hegemony, allowing them to interact in relative safety and protected by Honor Guards.