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6 Degrees of Movement in a virtual world

A simple explanation as to Degrees of Movement in a virtual world.

The difference between 3 degree and 6 degree movement in virtual reality has to do with how a user’s movement in the real world corresponds to movement within the virtual world.

Essentially it is a function of the headsets na dhow the positional tracking interprets movement. All VR headsets have some type of positional tracking and there is a significant disparity between how different models work. Tracking functionality can generally be broken down into three distinct categories, chiefly distinguished by the ‘Degrees of Freedom’ they offer.

3 Degrees of Freedom (DoF)

Headsets with Three Degrees of Freedom (3DoF) tracking:

All phone-based VR headsets including Google Cardboard, Samsung Gear VR, Google Daydream, as well as some standalone headsets such as Oculus Go.

3 degrees of freedom is the simplest form of user tracking in virtual reality and relies entirely on the inbuilt accelerometers, gyroscopes and magnetometers which phones use to measure movement. These tools  measure how a device is moving in three types of directional rotation (aka 3DoF) and movements are registered by the sensors and translated so the VR program can respond.

Roll is where the head pivots side to side (i.e. when looking around a corner)

 

Pitch is where the head tilts along a vertical axis (i.e. looking up or down).

Yaw is where the head swivels on the horizontal axis (i.e. looking left or right)

2.    6 of Freedom (DoF) – Rotational and Translation movement

Headsets that use six Degrees of Freedom (6DoF) tracking:

PC-based headsets including Oculus Rift, HTC Vive, Windows Mixed Reality.

A more sophisticated version of positional tracking is 6 Degrees of Freedom (DoF), which incorporates the 3 rotational measurements (rolling, pitching and yawing) and adds 3 further directional movements allowing a person to move around in a virtual space, rather than simply standing in one spot.

This type of tracking is crucial for whole-room VR experiences and affords the user far more freedom to explore VR environments and to better interact with the virtual world.

With 6 Degrees of Freedom (6DoF) both the headset and the controllers worn by the user are tracked. This can be achieved either by using external sensors to capture movement (known as outside-in tracking) or using sensors attached to the headset itself (called inside-out tracking) which continuously relays the positions of the headset and controllers back to the computer.

Elevation is where a person moves up or down (i.e. when bending down or standing up)

Strafe is where a person moves left or right (i.e. when sidestepping)

Surge is where a person moves forwards or backwards (i.e. when walking)

3.    3 and 6 Degrees of Freedom (DoF) – Hybrid tracking

With a number of wireless headsets on the horizon, attention has turned to a hybrid positional tracking system, whereby the headset offers 6 Degrees of Freedom (6DoF) but the controllers can only recognise 3 Degrees of Freedom (3DoF).

This reduction in handheld controller tracking is a result of prioritising the movement of the headset and although it won’t offer quite the same functionality as a 6DoF controller, it does allow standalone VR to offer an almost-comparable experience while reducing the amount of processing power required.

Choosing the right headset for your needs

Deciding on which headset suits your needs will depend on the end application. For a stationary experience such as A VR technology demonstration or something like viewing a home being sold off-plan, a 3 DoF headset might be suitable. However, for any VR experience where the user needs to have the freedom of exploration, 6 DoF tracking becomes a necessity.

It is always worth discussing your needs with your VR design team before deciding on one or the other, as they might be able to find an innovative solution for what you’re looking to achieve.