Tangible Augmented Reality for Computer Games
 |
Tangible Augmented Reality is a combination of a tangible user interface and an augmented reality system. During this project a
tangible user interface was developed for the studierstube and its suitability for computer games was investigated. The use of an
augmented reality system allows players to see a three-dimensional presentation of the graphics. Moreover, the specific interface
makes it possible to manipulate the pieces in a direct and intuitive way - instead of using a mouse or a keyboard. In order to
examine for which types of games and which types of manipulation this interface can be used, several versions of a computer game
have been implemented. The Tangible Augmented Reality System turned out to be well suited to both action games and strategy games.
However, the comparison of different types of manipulation showed that they can be handled more easily the closer they are to
real-world forms of manipulation.
|
Downloads
Master's Thesis of Christiane Ulbricht: Tangible Augmented Reality for Computer Games
Paper at VIIP 2003: Tangible Augmented Reality for Computer Games
Technical Report:
Video:
The Interface
Tangible Augmented Reality tries to eliminate the gap between the interaction with a natural environment and the interaction with
a computer system. A Tangible User Interface (TUI) uses objects of the natural environment as an interface to the computer. Thus,
the real world and the virtual world are combined. This intuitive way of interaction simplifies the communication between man and
machine, especially for unpractised users. Moreover, a TUI can be used by several persons because it is not restricted to one screen
or one keyboard. Especially computer games benefit from a three-dimensional presentation and a direct way of interaction because this
increases the realism of a game and simplifies its controls.
The design goals of the new interface have been the following:
- Marker-based optical tracking is used for the manipulation of the virtual objects.
- The markers should always be visible to the camera.
- The users should not be restricted in their freedom of movement and action.
To avoid the occlusion of markers, it has to be guaranteed that persons or materials cannot get between the camera and the markers.
This can be achieved by the use of a glass table. The camera is mounted underneath the table. The markers lie on the top of the table
- upside down, so that they can be tracked by the camera. The virtual objects are displayed on the top of the corresponding markers.
The users wear see-through HMDs to view the virtual objects. The table top is made of plexiglass framed by wood and mounted on legs.
The height of the legs can be altered so that players can stand or sit around the table.
|
 |
The Game
The Tabletop Game is implemented as a two player game. The players sit or stand around the glass table. Each player has a catapult
and a fixed number of balloons. The goal of the game is to shoot the opponent's balloons. The player who first manages to shoot all
the opponent's balloons wins the game. A player can control position and orientation of the catapult but not of the balloons.
Additionally, each player owns a windmill which provides him with the capability to move the balloons out of the line of fire of
the opponent. The mode of interaction is that the balloons are drifting with the wind that is produced by the windmill. To investigate
which type of game suits best for a TAR system, various types of the game and the controls have been implemented.
Various Types of the Game
The user can choose between one of the following types of the game:
- action game
- strategy game
In the action game mode both players can move their pieces at the same time. The effects of a move can be seen immediately. The main
focus of this mode are speed, a good aim and good spatial orientation capabilities of the players. The strategy game is turn based,
which means that a player has the possibility to try out several moves before she/he actually chooses one.
Various Types of Control
The catapults and the windmills are controlled through markers, which means that moving a marker on the table results in a movement
of the corresponding catapult or windmill. Since each of these pieces has a seperate marker, this system differs from conventional
computer games where several pieces are controlled through a single input device and where the player has to specify the piece she/he
likes to control. In the tabletop game this specification is simply done through choosing a marker.
However, it is not always desired to map the movement of a marker directly to the corresponding piece. Therefore, the Tabletop Game
provides two different ways to change the position and the direction of a piece:
- Moving a marker immediately causes an alteration of the position and orientation of the corresponding piece.
- While a marker is being moved, the piece follows the marker with a constant speed.
Results
Using our Tangible User Interface evokes the following advantages:
- Virtual objects become tangible.
- It is a wireless interaction.
- The amount of available input devices increases.
To interact with our system, a user does not have to learn an interaction technique because she/he can interact with the virtual
world in the same way she/he does with a natural environment. The selection and manipulation of virtual objects happens through markers.
Another advantage of the Tabletop Game is the absence of wires. Many VR input devices have to be physically connected to the computer
system. For example, the usage of a Pen & Tablet technique leads to two additional wires between the user and the system. Thus, the
freedom of movement of the user is quite limited. We avoided additional wires by using marker-based optical tracking.
Neither the operating system nor the number of ports limit the number of possible input devices. Just the number of markers that
can be tracked by the camera is an upper bound to the number of input devices. If we want to increase the number of players in the
Tabletop Game we just have to add an according number of markers. There is no need to buy and install additional input devices.
Conclusions
The aim of the Tabletop Game Interface is to evoke the impression of playing with a real-world board game while enjoying the possiblities
of a computer game. Thus, it unifies the advantages of computer games and board games. Computer games impress the player with appealing
animations, whereas board games provide an easy way of interaction. The Tabletop Game offers both, animations and an intuitive way of
interaction. Moreover, it is possible to include the third dimension in a natural way as can be seen through the interaction with the
terrain and the balloons.
|
