Degrees of freedom

Degrees of freedom or DOF is the ways an object can move within a space. There are a total of 6 degrees of freedom in a 3 dimensional space. The 6 DOF can be divided into 2 categories, rotational movements and translational movements. Each category has 3 DOF. Oculus Rift and SteamVR HMDs all have 6 DOF.

Rotational Movements

The 3 rotational movements are pitch, yaw, and roll. These movements are tracked by most HMDs' on-board sensors. As your head rotates forward, backward and side to side, the HMD senses the movements and alters its display accordingly.

Translational Movements

The 3 translational movements are left/right, forward/backward and up/down. These movements are usually tracked by an external camera or other sensors. Few HMDs use on-board sensors to track translational movements.