Saturday, October 2, 2010

What is 6DoF?

Six Degrees of Freedom


     6DoF was a term coined by Interplay for Descent in video games. Seeing as it was the first game to promote such, because the user was able to control these axis. And unless you're givin strict control over that axis it is not a Freedom, but a limitation. Thus not all game give you any control over all of these axis.

     Notice how Luner Lander or Asteroids is only 2DOF. Because the user is only given control over two of the axis. You can go diagonally but that doesn't justify more Degrees of Freedom.

From wiki, By definition 6DOF is:

     "Six degrees of freedom (6DoF) refers to motion of a rigid body in three-dimensional space, namely the ability to move forward/backward, up/down, left/right (translation in three perpendicular axes) combined with rotation about three perpendicular axes (pitch, yaw, roll). As the movement along each of the three axes is INDEPENDANT of each other and independent of the rotation about any of these axes, the motion indeed has six degrees of freedom."

     Notice I put the keyword in caps. Some game engines don't allow for full 6DOF movement even, and must have fake ways of implamenting certain features like leaning in some FPS. Perhaps you can move in these fashions but in limited ways, for example you can crouch and jump, but you can't nessesarily fly, and if you fly in most cases (like DragonBallZ) you cant bank.


     There are many claims made by people that certain devices will be six degrees of freedom when in fact they are not.  A few easy to mistake objects are Helicopters, or Harrier Jets.  I have a radio controlled helicopter. And understand the troubles of this 6DoF.  The Helicopter isn't free do move on every axis, but uses it's momentum to slide into them while switching control of the axis.  A Helicopter is a simulated 4DoF device or a true 2DoF device:


1DOF - Up and down from the top rotor spinning. And blades moving. (TRUE)
2DOF - The tilt forward and back from the top rotor for simulated movement forward (notice this is a limited movemnt and if held too long will serve as pitch)
3DOF - The tilt side to side of the top rotor for simulated movment from side to side (notice this is also a limtited movment and if held too long will serve as bank)
4DOF - The tail rotor which rotates the helicopter's heading. Either on lower or higher timing than the top rotor sync.  (TRUE)



     Notice without the top rotor the function of the rest of the freedoms fail.  Thus only true freedoms are the top rotor spinning, and the required tail rotor to keep you from spinning and making the top rotor functional.


     With airplanes it's worse, where there is only one functional freedom, Thrust.  Forward for true 1DoF, and simulated banking, heading, and yaw for 4DoF but only when moving.  The Harrier Jet doesn't have more freedoms, it has to reroute it's engines from back thrust to down thrust to hover, so the amount of freedoms stay the same.  Unless it could thrust forward and up at the same time.  In which case it's 2DoF still because the pilot wouldn't bank when that's happening... 


     There is no current known object that does true 6DoF, and if most people saw one, pilots included, they would claim it's a UFO.  Unless we somehow have figured out anti-gravity and enough renewable energy to support it.


     Trichording is a movement that is only possible in 6DoF environments.  This is the ultimate skill in a 6DoF world, and is similar to strafe running.  However instead of moving in one diagonal direction, you move in three.


From a Miner Wars forum thread: Here

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