While the information that is displayed on the HUD depends greatly on the game, there are many features that players recognize across many games. Common features include:
There are also trends common among genres and platforms. Many online games show player names and a chat text box for talking to the other players. RTS games tend to have complex user interfaces, with context-sensitive panels and a full-overview mini-map with fog of war.
Armour levels are also commonly monitored, either through a separate readout, or as part of the health system. For example, Halo 2 uses one recharging shield bar, acting as the health level. When this is depleted the player can only take a few more hits before death. The same goes in Destroy All Humans!, but in the form of Crypto's shields. Traditionally, games used lives to represent health. Every time the main character was injured he would lose one of his limited lives. Another way to display the life in the HUD is demonstrated in Gears of War, where the characters life is only displayed when he is under attack and a cog begins to appear on the screen. The fuller the cog, the closer to death the character is, this cog slowly disappears from the HUD as health is regained. This particular health system is sometimes called the "Red ring" system.
There is also a lot of variance with regards to the display of other information. Some games permanently display all the weapons a character is currently carrying, others rely on a pull up weapon selector. Inventory or storage space may also be permanently overlaid over the screen, or accessed via a menu. Alternatively, only a limited number of items stored in the inventory might be displayed at once, with the rest being rotated into view using the [ and ] keys.
In order to maintain the suspension of disbelief, some games make the HUD look like a real HUD within the context of the game's world. Many first-person vehicle simulation games use this technique, showing instruments and displays that the driver of the vehicle would be expected to see. The displays in the helmet in the first-person adventure game Metroid Prime also mimic the player's point of view. A similar method is used in the game Tom Clancy's Ghost Recon Advanced Warfighter. It should perhaps be noted that in some of these circumstances where the player and character within the game are meant to see the same 'HUD' information, Halo for example, the term HMD (Helmet Mounted Display) would technically be more accurate. This is not to be confused with Head-Up Display.
Some games provide the player with an option to hide part or all of the HUD. This is usually used to create cleaner looking screenshots and videos, which can be essential to producing machinima. Certain games like Pac-Man World and Super Mario Galaxy even keep the HUD elements off-screen without any option. When this method is used, they will only appear when affected. In some games, they can temporarily be displayed all at once with the press of a button. In games where that method is not used, the only way to display them at once is by pausing the game.
A few games give players extensive control over their HUD, such as customizing position, size, color, and opacity. World of Warcraft is notable for allowing players to significantly modify and enhance the user interface through Lua scripting.
Despite the modern dominance of 3D graphics in games, HUDs are frequently rendered with a 2D look, often using sprites.
Sometimes information normally displayed in the HUD is instead disguised as part of the scenery or vehicle the player is travelling in. For example when the player is driving a car that can sustain a certain number of hits, a smoke trail might appear when the car can take only two more hits, fire might appear from the car to indicate that the next hit will be fatal. Wounds and bloodstains may sometimes appear on injured characters who may also limp, stagger, slouch over or breath heavily to indicate they are injured.
In rare cases, no HUD is used at all, leaving the player to interpret the auditory and visual cues in the gameworld. The elimination of elements has hardly become a trend in game development nowadays, but can be witnessed in several titles as of late. Some classic examples of games without HUDs are Silent Hill 2, Jurassic Park: Trespasser, Ico, The Getaway, Another World, King Kong, and Call of Cthulhu: Dark Corners of the Earth.
Upcoming games that promise no HUD include Mirror's Edge, Sadness, Aliens: Colonial Marines, and Champions Online, although this game is not completely HUDless. The science fiction third-person thriller Dead Space also promises a non-HUD experience...all of the in-game menus and health/weapon information is displayed on Issac's suit, or in holograms that are projected from it.
This is also particularly true with plasma display technology, because of their high risk of burn-in. This could occur with just several hours of displaying the same image or part of image.
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