Lecture 7 - Mixed Reality Tracking

Question 1

What is the goal of mixed reality?

Answer 1

To combine reality and virtuality.

Question 2

To achieve this goal what do we need to ensure?

Answer 2

That the content appears at the right place and time (natural places relative to the user). This means we need to establish a relationship between the user and virtual environment.

Question 3

What kind of tracking can we use in mixed reality?

Answer 3

• rotation tracking (gyroscpoe)
• position tracking (accelerometer)
• controller tracking
• hand tracking

Question 4

What are the degrees of freedom?

Answer 4

Defines how many independent ways a dynamic system can move. In mixed reality this would include:
- Translation (position) -> 3 ways
- Rotation (orientation) -> 3 ways

Question 5

What is 0DOF?

Answer 5

No tracking at all

Question 6

What is 3DOF?

Answer 6

Usually orientation only tracking. This can track where the user is looking, but not where the head is positioned. This is done with IMU.

Question 7

What is 6DOF?

Answer 7

Both orientation and position tracking. This can track where the user is looking and the position of the head. Done with IMU + SLAM (fusion of orientation and position tracking).

Question 8

What is IMU?

Answer 8

Internal measurement unit. It is an electronic device that measures and reports acceleration, orientation, angular rates, and other gravitational forces.

Question 9

Another name for 6DOF?

Answer 9

room-scale tracking

Question 10

What is SLAM?

Answer 10

SLAM stands for simultaneous localisation and mapping (sometimes called synchronised localisation and mapping). It is the process of mapping an area whilst keeping track of the location of the device within that area. This is what makes mobile mapping possible.

Question 11

2 Types of Tracking Implementation (in device or outside)?

Answer 11

• inside out tracking
• outside in tracking

Question 12

Inside out tracking?

Answer 12

Tracking capabilities within the device
* e.g., SLAM + controller/hand tracking

• sensors are relative to user

Question 13

Outside in tracking?

Answer 13

Use external devices to track position

Example: HTC/Valve Lighthouse Tracking
* External “lighthouse” laser emitters
* Alternate horizontal/vertical sweeps
* Headset and controllers detect the lasers

Example: motion capture (e.g., OptiTrack)
* External sensors look for markers on the user

Question 14

Inside Out Advantages and Disadvantages?

Answer 14

+:
- self-contained
- fully mobile, so user can go anywhere

-:
- tracking quality can vary
- can only detect relative positioning

Question 15

Outside in Advantages and Disadvantages?

Answer 15

+:
- excelllent tracking overall
- provides absolute positioning
- good for tracking multiple people

-:
- requires external devices
- limited range
- semi-permanent setup

Question 16

Why is tracking necessary for mixed reality?

Answer 16

so we can achieve perspective-dependent rendering, where we render things with respect to the user -> increasing usability