Understanding the Six Degrees of Freedom

Let’s get started thinking about the six degrees of freedom (6DoF) by using a simple visualization exercise. Imagine that you’re in a small cottage in the woods. There are fruit and flowers on a table in front of you, and windows on three sides. Through the front window are trees framed by blue sky. Look around the room and take it all into view. Turn your head left to right to observe the room and the tabletop spread, looking down at the wood floor then up to the ceiling. Standing tall, you can see over the vase of flowers to check out a trail through the woods. Just outside the window, a blue jay takes flight. At a glance you can tell the jay is close. Pitch your gaze back down to the tabletop, then shift your head to the side to reveal an apple hidden by the vase.

In addition to visualizing that experience in the cottage, you used all six degrees of freedom to observe the scene around you. Each of your head movements could be tracked across three axes (X, Y, Z), translating along, and rotating around them, in combination, to provide a complete view in every direction and at every angle. Additionally, each of your eyes received a slightly different point of view, offset by the distance between your left and right eyes. This slight difference between each eye view (binocular disparity) is what enables you to perceive distance and sense whether objects were close or far.

Without thinking about it, we use 6DoF every day. It helps us navigate through our world, and casually observe everything that we encounter. Without 6DoF, our experience would be very different.

This brief explainer video with one of our Lytro Engineers is an easy to understand primer on the six degrees of freedom.

In this article, we’re going provide examples of each of the six degrees to help you easily identify them. This will be really useful in understanding what you’re experiencing both in the real world and the virtual one in a VR headset. The six degrees of freedom are:

  1. Rotate horizontally side-side (yaw)
  2. Rotate vertically up/down (pitch)
  3. Rotate gaze at an angle (roll)
  4. Move left/right (slide or sway)
  5. Move up/down (heave)
  6. Move forward/backward (surge)

The first three degrees of freedom are rotation around an axis. Those rotations are easily tracked by mobile based VR systems like Cardboard or GearVR. The second three degrees are referred to as translational moves along an axis which require a VR system with support for positional tracking like Oculus Rift, HTC Vive or Playstation VR.

To help illustrate each degree of freedom, we’ve created these six simple animations with each degree isolated to show its characteristics.

1. Yaw is the horizontal rotation of your head

Observation: Note that objects in the scene are not moving in relation to each other as rotation does not result in any parallax

2. Pitch is rotating your head to look up or down

Observation: Note that objects in the scene are not moving in relation to each other as rotation does not result in any parallax

3. Roll happens when you tilt your head side to side.

Observation: Note that objects in the scene are not moving in relation to each other as rotation does not result in any parallax

4. Shift or slide your head left/right along the horizontal axis

Observation: Note that objects that are closer to the viewer are moving faster than objects that are further away from the viewer. This motion is referred to as Parallax and is a key visual cue for the brain to understand the world around us.

5. Rise up or slouch down

Observation: Note that objects that are closer to the viewer are moving faster than objects that are further away from the viewer. This motion is referred to as Parallax and is a key visual cue for the brain to understand the world around us.

6. Lean forward, pull back

Observation: Note that objects that are closer to the viewer are moving faster than objects that are further away from the viewer. This motion is referred to as Parallax and is a key visual cue for the brain to understand the world around us.

About Steve Cooper 5 Articles
Director Product Marketing at Lytro, cyclist and owns a flame thrower

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