Invisible wall

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An invisible wall is a video game term for a boundary that limits where a player can go, but doesn't appear in-game as any kind of visible obstacle, or as an obstacle that in reality could easily be bypassed, such as a mid-sized rock or short fence. In 2D games, the edge of the screen itself can form an "invisible wall", in that a character in play may be prevented from travelling off the edge of the screen. In 3D games, invisible walls are used similarly to prevent a player leaving the game-play area. This is often done in preference to using a more visible boundary, as this can reduce the realism of the environment.

[edit] Related errors

In some games, errors in the programming, or use of computer game cheats can result in the wall becoming penetrable. If a user passes through the wall, they may enter an area of the game not intended for their use, for example an area containing unused items or portions of a level; or the user may find themselves reappearing on the opposite side of the game-play area. Alternatively, a run-time error could occur.

[edit] Examples

Some examples of invisible walls include:

• In the 3D First person shooter game Doom, using a "no clipping" cheat enables the player to freely move not only around the visible part of the current map, but even beyond it, at least up to the limit imposed by the coordinate system of the game itself, which is the only true "invisible barrier". In the latter case, the first person perspective display becomes corrupt, while the map mode still correctly tracks the player's movements.

• In the vertically scrolling NES game Front Line, due to a programming glitch the player can continue moving sideways of the screen beyond the intended "playfield" area, causing the graphic tiles to become corrupted and enabling the player to slip past most enemies, who won't follow him into the glitchy "void". The actual "invisible wall" is not where the player is (normally) supposed to be playing, but extends farther to the left and right sides of the screen.

• Also, in the game Battlefield 1942, while a player is normally prevented from exiting a map's boundaries with a timed death penalty, in certain circumstances those barriers can be violated (e.g. by using the free flying camera mode, using an unusually high speed vehicle or finding an unusually "thin" boundary area) and will result in a map wrap-around effect (the player will emerge on the oppossing part of the map).

• In the Tony Hawk Pro Skater video games, large indoor and outdoor areas are featured. While indoor areas have logical walls to confine the player, outdoor areas often use an invisible line. Rather than an actual barrier, the skater will 'bail' from his or her board, an error message is displayed, and the skater will be reset at a certain point.

• In the game Grand Theft Auto 3, many large buildings are incomplete and do not have a roof. These are normally not accessible, but through the use of cheats, the player can reach these spots. When you go into the top of one of these roofless buildings, everything will spin around you, and the city will appear upside down momentaraly while you are falling towards it. When it all ends, you will be back on the streets below.