Virtual camera system
Encyclopedia
Virtual world
A virtual world is an online community that takes the form of a computer-based simulated environment through which users can interact with one another and use and create objects. The term has become largely synonymous with interactive 3D virtual environments, where the users take the form of...
. Camera systems are used in videogames where their purpose is to show the action at the best possible angle; more generally, they are used in 3D virtual worlds when a third person view is required.
As opposed to film makers, virtual camera system creators have to deal with a world that is interactive and unpredictable. It is not possible to know where the player's character
Player character
A player character or playable character is a character in a video game or role playing game who is controlled or controllable by a player, and is typically a protagonist of the story told in the course of the game. A player character is a persona of the player who controls it. Player characters...
is going to be in the next few seconds; therefore, it is not possible to plan the shots as a film maker would do. To solve this issue, the system relies on certain rules or artificial intelligence
Artificial intelligence
Artificial intelligence is the intelligence of machines and the branch of computer science that aims to create it. AI textbooks define the field as "the study and design of intelligent agents" where an intelligent agent is a system that perceives its environment and takes actions that maximize its...
to select the most appropriate shots.
There are mainly three types of camera systems. In fixed camera systems, the camera does not move at all and the system displays the player's character in a succession of still shots. Tracking cameras, on the other hand, follow the character's movements. Finally, interactive camera systems are partially automated and allow the player to directly change the view. To implement camera systems, video game developers use techniques such as constraint solvers
Constraint programming
Constraint programming is a programming paradigm wherein relations between variables are stated in the form of constraints. Constraints differ from the common primitives of imperative programming languages in that they do not specify a step or sequence of steps to execute, but rather the properties...
, artificial intelligence scripts
Scripts (artificial intelligence)
Scripts were developed in the early AI work by Roger Schank, Robert P. Abelson and their research group, and are a method of representing procedural knowledge...
, or autonomous agent
Autonomous agent
An autonomous agent is an intelligent agent operating on an owner's behalf but without any interference of that ownership entity. An intelligent agent, however appears according to a multiply cited statement in a no longer accessible IBM white paper as follows:Intelligent agents are software...
s.
Third-person view
In video games, "third person" refers to a graphical perspectivePerspective (visual)
Perspective, in context of vision and visual perception, is the way in which objects appear to the eye based on their spatial attributes; or their dimensions and the position of the eye relative to the objects...
rendered from a fixed distance behind and slightly above the player character. This viewpoint allows players to see a more strongly characterized avatar
Avatar (computing)
In computing, an avatar is the graphical representation of the user or the user's alter ego or character. It may take either a three-dimensional form, as in games or virtual worlds, or a two-dimensional form as an icon in Internet forums and other online communities. It can also refer to a text...
, and is most common in action game
Action game
Action game is a video game genre that emphasizes physical challenges, including hand–eye coordination and reaction-time. The genre includes diverse subgenres such as fighting games, shooter games, and platform games, which are widely considered the most important action games, though some...
s and action adventure games. Games with this perspective often make use of positional audio, which the volume of ambient sounds varies depending on the position of the avatar.
There are primarily three types of third-person camera systems: the "fixed camera systems" in which the camera positions are set during the game creation; the "tracking camera systems" in which the camera simply follows the player's character; and the "interactive camera systems" that are under the player's control.
Fixed
Alone in the Dark (video game)
Alone in the Dark is a 1992 survival horror video game developed by Infogrames. The game has spawned several sequels as part of the Alone in the Dark series , and was one of the first survival horror games, after the 1989 Capcom game, Sweet Home...
. While the characters are in 3D, the background on which they evolve has been pre-rendered. The early Resident Evil games are notable examples of games that use fixed cameras.
One advantage of this camera system is that it allows the game designers to use the language of film
Film theory
Film theory is an academic discipline that aims to explore the essence of the cinema and provides conceptual frameworks for understanding film's relationship to reality, the other arts, individual viewers, and society at large...
. Indeed, like filmmakers, they have the possibility to create a mood through camerawork and careful selection of shots. Games that use this kind of technique are often praised for their cinematic qualities. For example, Capcom
Capcom
is a Japanese developer and publisher of video games, known for creating multi-million-selling franchises such as Devil May Cry, Chaos Legion, Street Fighter, Mega Man and Resident Evil. Capcom developed and published Bionic Commando, Lost Planet and Dark Void too, but they are less known. Its...
uses this technique in Resident Evil 2
Resident Evil 2
Resident Evil 2, known as in Japan, is a survival horror video game originally released for the PlayStation in 1998. Developed by Capcom as the second installment in the Resident Evil series, its story takes place two months after the events of the first game, Resident Evil...
in which the encounter between a monster and Leon is introduced by a careful selection of views that aim at creating tension.
Tracking
As the name says, a tracking camera follows the characters from behind. The player does not control the camera in any way - he/she cannot for example rotate it or move it to a different position. This type of camera system was very common in early 3D games such as Crash BandicootCrash Bandicoot
Crash Bandicoot may refer to:* Crash Bandicoot , a video game protagonist* Crash Bandicoot , a video game series* Crash Bandicoot , a 1996 PlayStation video game and first Crash Bandicoot...
or Tomb Raider
Tomb Raider
Tomb Raider is an action-adventure video game developed by Core Design and published by Eidos Interactive. It was originally released in 1996 for the Sega Saturn, with MS-DOS and PlayStation versions following shortly thereafter...
since it is very simple to implement. However, there are a number of issues with it. In particular, if the current view is not suitable (either because it is occluded by an object, or because it is not showing what the player is interested in), it cannot be changed since the player does not control the camera. Sometimes this viewpoint causes difficulty when a character turns or stands face out against a wall. The camera may jerk or end up in awkward positions.
Implementation
There is a large body of research on how to implement a camera system . The role of a constraint solver softwareConstraint programming
Constraint programming is a programming paradigm wherein relations between variables are stated in the form of constraints. Constraints differ from the common primitives of imperative programming languages in that they do not specify a step or sequence of steps to execute, but rather the properties...
is to generate the best possible shot given a set of visual constraints. In other words, the constraint solver is given a requested shot composition such as "show this character and ensure that he covers at least 30 percent of the screen space". The solver will then use various methods to try creating a shot that would satisfy this request. Once a suitable shot is found, the solver outputs the coordinates and rotation of the camera, which can then be used by the graphic engine renderer to display the view.
In some camera systems, if no solution can be found, constraints are relaxed. For example, if the solver cannot generate a shot where the character occupies 30 percent of the screen space, it might ignore the screen space constraint and simply ensure that the character is visible at all. Such methods include zooming out.
Some camera systems use predefined scripts to decide how to select the current shot. Typically, the script is going to be triggered as a result of an action. For instance, when the player's character initiates a conversation with another character, the "conversation" script is going to be triggered. This script will contain instructions on how to "shoot" a two-character conversation. Thus the shots will be a combination of, for instance, over the shoulder shot
Over the shoulder shot
In film or video, an over the shoulder shot is a shot of someone or something taken from the perspective or camera angle from the shoulder of another person. The back of the shoulder and head of this person is used to frame the image of whatever the camera is pointing toward...
s and close-up
Close-up
In filmmaking, television production, still photography and the comic strip medium a close-up tightly frames a person or an object. Close-ups are one of the standard shots used regularly with medium shots and long shots . Close-ups display the most detail, but they do not include the broader scene...
shots. Such script-based approaches usually rely on a constraint solver to generate the camera coordinates.
Bill Tomlinson used a more original approach to the problem. He devised a system in which the camera is an autonomous agent
Autonomous agent
An autonomous agent is an intelligent agent operating on an owner's behalf but without any interference of that ownership entity. An intelligent agent, however appears according to a multiply cited statement in a no longer accessible IBM white paper as follows:Intelligent agents are software...
with its own personality. The style of the shots and their rhythm will be affected by its mood. Thus a happy camera will "cut more frequently, spend more time in close-up shots, move with a bouncy, swooping motion, and brightly illuminate the scene".
In mixed-reality applications
In 2010, the Kinect was released by MicrosoftMicrosoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
as a 3D scanner
3D scanner
A 3D scanner is a device that analyzes a real-world object or environment to collect data on its shape and possibly its appearance . The collected data can then be used to construct digital, three dimensional models....
/webcam
Webcam
A webcam is a video camera that feeds its images in real time to a computer or computer network, often via USB, ethernet, or Wi-Fi.Their most popular use is the establishment of video links, permitting computers to act as videophones or videoconference stations. This common use as a video camera...
hybrid peripheral device which provides full-body detection of Xbox 360
Xbox 360
The Xbox 360 is the second video game console produced by Microsoft and the successor to the Xbox. The Xbox 360 competes with Sony's PlayStation 3 and Nintendo's Wii as part of the seventh generation of video game consoles...
players and hands-free control of the user interfaces of video games and other software on the console. This was later modified by Oliver Kreylos of University of California, Davis
University of California, Davis
The University of California, Davis is a public teaching and research university established in 1905 and located in Davis, California, USA. Spanning over , the campus is the largest within the University of California system and third largest by enrollment...
in a series of YouTube videos which showed him combining the Kinect with a PC-based virtual camera. Because the Kinect is capable of detecting a full range of depth (through computer stereo vision
Computer stereo vision
Computer stereo vision is the extraction of 3D information from digital images, such as obtained by a CCD camera. By comparing information about a scene from two vantage points, 3D information can be extracted by examination of the relative positions of objects in the two panels...
and Structured light
Structured light
]Structured light is the process of projecting a known pattern of pixels on to a scene. The way that these deform when striking surfaces allows vision systems to calculate the depth and surface information of the objects in the scene, as used in structured light 3D scanners.Invisible Structured...
) within a captured scene, Kreylos demonstrated the capacity of the Kinect and the virtual camera to allow free-viewpoint navigation of the range of depth, although the camera could only allow a video capture of the scene as shown to the front of the Kinect, resulting in fields of black, empty space where the camera was unable to capture video within the field of depth. Later, Kreylos demonstrated a further elaboration on the modification by combining the video streams of two Kinects in order to further enhance the video capture within the view of the virtual camera. Kreylos' developments using the Kinect were covered among the works of others in the Kinect hacking and homebrew
Homebrew (video games)
Homebrew is a term frequently applied to video games or other software produced by consumers to target proprietary hardware platforms not typically user-programmable or that use proprietary storage methods...
community in a New York Times article.