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Six degrees of freedom (6DOF) refers to the six mechanical degrees of freedom of movement of a
rigid body In physics, a rigid body (also known as a rigid object) is a solid body in which deformation is zero or so small it can be neglected. The distance between any two given points on a rigid body remains constant in time regardless of external force ...
in
three-dimensional space Three-dimensional space (also: 3D space, 3-space or, rarely, tri-dimensional space) is a geometric setting in which three values (called ''parameters'') are required to determine the position (geometry), position of an element (i.e., Point (m ...
. Specifically, the body is free to change
position Position often refers to: * Position (geometry), the spatial location (rather than orientation) of an entity * Position, a job or occupation Position may also refer to: Games and recreation * Position (poker), location relative to the dealer * ...
as forward/backward (surge), up/down (heave), left/right (sway)
translation Translation is the communication of the Meaning (linguistic), meaning of a #Source and target languages, source-language text by means of an Dynamic and formal equivalence, equivalent #Source and target languages, target-language text. The ...
in three
perpendicular In elementary geometry, two geometric objects are perpendicular if they intersect at a right angle (90 degrees or π/2 radians). The condition of perpendicularity may be represented graphically using the ''perpendicular symbol'', ⟂. It can ...
axes Axes, plural of '' axe'' and of '' axis'', may refer to * ''Axes'' (album), a 2005 rock album by the British band Electrelane * a possibly still empty plot (graphics) See also * Axess (disambiguation) *Axxess (disambiguation) Axxess may refer to ...
, combined with changes in
orientation Orientation may refer to: Positioning in physical space * Map orientation, the relationship between directions on a map and compass directions * Orientation (housing), the position of a building with respect to the sun, a concept in building de ...
through
rotation Rotation, or spin, is the circular movement of an object around a '' central axis''. A two-dimensional rotating object has only one possible central axis and can rotate in either a clockwise or counterclockwise direction. A three-dimensional ...
about three perpendicular axes, often termed yaw (normal axis), pitch (transverse axis), and roll (longitudinal axis). Three degrees of freedom (3DOF), a term often used in the context of
virtual reality Virtual reality (VR) is a simulated experience that employs pose tracking and 3D near-eye displays to give the user an immersive feel of a virtual world. Applications of virtual reality include entertainment (particularly video games), educ ...
, typically refers to tracking of rotational motion only: pitch, yaw, and roll.


Robotics

Serial and parallel manipulator systems are generally designed to position an
end-effector In robotics, an end effector is the device at the end of a robotic arm, designed to interact with the environment. The exact nature of this device depends on the application of the robot. In the strict definition, which originates from serial ro ...
with six degrees of freedom, consisting of three in translation and three in orientation. This provides a direct relationship between actuator positions and the configuration of the manipulator defined by its
forward Forward is a relative direction, the opposite of backward. Forward may also refer to: People * Forward (surname) Sports * Forward (association football) * Forward (basketball), including: ** Point forward ** Power forward (basketball) ** Sm ...
and
inverse kinematics In computer animation and robotics, inverse kinematics is the mathematical process of calculating the variable joint parameters needed to place the end of a kinematic chain, such as a robot manipulator or animation character's skeleton, in a g ...
.
Robot A robot is a machine—especially one programmable by a computer—capable of carrying out a complex series of actions automatically. A robot can be guided by an external control device, or the control may be embedded within. Robots may be c ...
arms are described by their degrees of freedom. This is a practical metric, in contrast to the abstract definition of degrees of freedom which measures the aggregate positioning capability of a system. In 2007,
Dean Kamen Dean Lawrence Kamen (born April 5, 1951) is an American engineer, inventor, and businessman. He is known for his invention of the Segway and iBOT, as well as founding the non-profit organization FIRST with Woodie Flowers. Kamen holds over 1, ...
, inventor of the
Segway The Segway is a two-wheeled, self-balancing personal transporter invented by Dean Kamen and brought to market in 2001 as the Segway HT, subsequently as the Segway PT, and manufactured by Segway Inc. ''HT'' is an initialism for "human transp ...
, unveiled a prototype robotic arm with 14 degrees of freedom for
DARPA The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the Adv ...
.
Humanoid robot A humanoid robot is a robot resembling the human body in shape. The design may be for functional purposes, such as interacting with human tools and environments, for experimental purposes, such as the study of bipedal locomotion, or for other pur ...
s typically have 30 or more degrees of freedom, with six degrees of freedom per arm, five or six in each leg, and several more in
torso The torso or trunk is an anatomical term for the central part, or the core, of the body of many animals (including humans), from which the head, neck, limbs, tail and other appendages extend. The tetrapod torso — including that of a human â ...
and
neck The neck is the part of the body on many vertebrates that connects the head with the torso. The neck supports the weight of the head and protects the nerves that carry sensory and motor information from the brain down to the rest of the body. In ...
.


Engineering

The term is important in
mechanical systems A machine is a physical system using power to apply forces and control movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to natural biological macromolecul ...
, especially biomechanical systems, for analyzing and measuring properties of these types of systems that need to account for all six degrees of freedom. Measurement of the six degrees of freedom is accomplished today through both AC and DC magnetic or electromagnetic fields in sensors that transmit positional and angular data to a processing unit. The data is made relevant through software that integrates the data based on the needs and programming of the users. The six degrees of freedom of a mobile unit are divided in two motional classes as described below. Translational envelopes: #Moving forward and backward on the X-axis. (Surge) #Moving left and right on the Y-axis. (Sway) #Moving up and down on the Z-axis. (Heave) Rotational envelopes: #Tilting side to side on the X-axis. (
Roll Roll or Rolls may refer to: Movement about the longitudinal axis * Roll angle (or roll rotation), one of the 3 angular degrees of freedom of any stiff body (for example a vehicle), describing motion about the longitudinal axis ** Roll (aviation), ...
) #Tilting forward and backward on the Y-axis. ( Pitch) #Turning left and right on the Z-axis. ( Yaw) In terms of a headset, such as the kind used for
virtual reality Virtual reality (VR) is a simulated experience that employs pose tracking and 3D near-eye displays to give the user an immersive feel of a virtual world. Applications of virtual reality include entertainment (particularly video games), educ ...
, rotational envelopes can also be thought of in the following terms: *Pitch:
Nodding A nod of the head is a gesture in which the head is tilted in alternating up and down arcs along the sagittal plane. In many cultures, it is most commonly, but not universally, used to indicate agreement, acceptance, or acknowledgement. To ...
"yes" *Yaw: Shaking "no" *Roll: Bobbling from side to side


Operational envelope types

There are three types of operational envelope in the Six degrees of freedom. These types are ''Direct'', ''Semi-direct'' (conditional) and ''Non-direct,'' all regardless of the time remaining for the execution of the maneuver, the energy remaining to execute the maneuver and finally, if the motion is commanded via a biological entity (e.g. human), a robotical entity (e.g. computer) or both. #''Direct type'': Involved a degree can be commanded directly without particularly conditions and described as a normal operation. (An
aileron An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement around ...
on a basic airplane) #''Semi-direct type'': Involved a degree can be commanded when some specific conditions are met. (
Reverse thrust Thrust reversal, also called reverse thrust, is the temporary diversion of an aircraft engine's thrust for it to act against the forward travel of the aircraft, providing deceleration. Thrust reverser systems are featured on many jet aircraft to ...
on an aircraft) #''Non-direct type'': Involved a degree when is achieved via the interaction with its environment and cannot be commanded. (Pitching motion of a vessel at sea) Transitional type also exists in some vehicles. For example, when the
Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program na ...
operates in space, the craft is described as fully-direct-six because its six degrees can be commanded. However, when the Space Shuttle is in the earth's atmosphere for its return, the fully-direct-six degrees are no longer applicable for many technical reasons.


Game controllers

''Six degrees of freedom'' also refers to movement in video game-play.
First-person shooter First-person shooter (FPS) is a sub-genre of shooter video games centered on gun and other weapon-based combat in a first-person perspective, with the player experiencing the action through the eyes of the protagonist and controlling the pl ...
(FPS) games generally provide five degrees of freedom: forwards/backwards, slide left/right, up/down (jump/crouch/lie), yaw (turn left/right), and pitch (look up/down). If the game allows leaning control, then some consider it a sixth DOF; however, this may not be completely accurate, as a lean is a limited partial rotation. The term ''6DOF'' has sometimes been used to describe games which allow freedom of movement, but do not necessarily meet the full 6DOF criteria. For example, ''
Dead Space 2 ''Dead Space 2'' is a 2011 survival horror game developed by Visceral Games and published by Electronic Arts. It was released for PlayStation 3, Windows, and Xbox 360 in January. The second mainline entry in the ''Dead Space (franchise), Dead Spa ...
'', and to a lesser extent, ''
Homeworld ''Homeworld'' is a real-time strategy video game developed by Relic Entertainment and published by Sierra Entertainment, Sierra Studios on September 28, 1999, for Microsoft Windows. Set in space, the science fiction game follows the Kushan exil ...
'' and ''
Zone Of The Enders is a video game franchise created by Hideo Kojima and Konami that focused around combat in space with mecha called Orbital Frames. The original ''Zone of the Enders'' was released for the PlayStation 2 in March 2001. A sequel, '' Zone of the ...
'' allow freedom of movement. Some examples of true 6DOF games, which allow independent control of all three movement axes and all three rotational axes, include ''
Elite Dangerous ''Elite Dangerous'' is a space flight simulation game developed and published by Frontier Developments. The player takes the role of a pilot (colloquially referred to as "Commander" or "CMDR") of a spaceship, and explores a realistic 1:1 scale, ...
'', ''
Shattered Horizon ''Shattered Horizon'' is a 2009 first-person shooter video game developed and published by Futuremark Games Studio. The game was released on November 4, 2009 exclusively on Microsoft Windows via Steam. Gameplay ''Shattered Horizon'' is a fir ...
'', the ''
Descent Descent may refer to: As a noun Genealogy and inheritance * Common descent, concept in evolutionary biology * Kinship, one of the major concepts of cultural anthropology **Pedigree chart or family tree ** Ancestry ** Lineal descendant **Heritag ...
'' franchise, ''
Retrovirus A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. Once inside the host cell's cytoplasm, the virus uses its own reverse transcriptase ...
'', ''
Miner Wars ''Miner Wars 2081'' is a six degrees of freedom action-survival space-shooter simulation game produced by Keen Software House. The gameplay offers a choice of single player, co-op, and deathmatch multi-player. The game is set in the year 2081, ...
'', '' Space Engineers'', '' Forsaken'' and '' Overload'' (from the same creators of ''Descent''). The space MMO ''
Vendetta Online ''Vendetta Online'' is a Twitch gameplay, twitch-based, science fiction massively multiplayer online role-playing game (MMORPG) developed by Guild Software for the operating systems Android (operating system), Android, Linux, Mac OS X, iOS, and M ...
'' also features 6 degrees of freedom. Motion tracking hardware devices such as
TrackIR TrackIR is an optical motion tracking game controller for Microsoft Windows created by NaturalPoint Inc.. TrackIR tracks head motions with up to six degrees of freedom (6DOF) in later models, allowing handsfree view control for improved game im ...
and software-based apps lik
Eyeware Beam
are used for 6DOF head tracking. This device often finds its places in
flight simulators A flight simulator is a device that artificially re-creates aircraft flight and the environment in which it flies, for pilot training, design, or other purposes. It includes replicating the equations that govern how aircraft fly, how they rea ...
and other vehicle simulators that require looking around the cockpit to locate enemies or simply avoiding accidents in-game. The acronym 3DOF, meaning movement in the three dimensions but not rotation, is sometimes encountered. The
Razer Hydra The Razer Hydra (previously known as Sixense TrueMotion) is a motion and orientation detection game controller developed by Sixense Entertainment, a company founded in 2007, in partnership with Razer USA. It uses a weak magnetic field to detect ...
, a motion controller for PC, tracks position and rotation of two wired nunchucks, providing six degrees of freedom on each hand. The SpaceOrb 360 is a 6DOF computer input device released in 1996 originally manufactured and sold by the SpaceTec IMC company (first bought by
Labtec Labtec Inc. was a manufacturer of computer accessories, founded in Vancouver, Washington, United States in 1982. They were best known for their budget range of peripherals such as keyboards, mice, microphones, speakers and webcams. Originall ...
, which itself was later bought by
Logitech Logitech International S.A. ( ; often shortened to Logi) is a Swiss multinational manufacturer of computer peripherals and software, with headquarters in Lausanne, Switzerland, and Newark, California. The company has offices throughout Europe, ...
). The controllers sold with HTC VIVE provide 6DOF information by the lighthouse, which adopts Time of Flight (TOF) technology to determine the position of controllers.


See also

* * * * * *


References

{{DEFAULTSORT:Six Degrees Of Freedom Mechanics Biomedical engineering Video game gameplay Robot kinematics