3 Commando Brigade

Head tracking. The easy and *Cheap way.

* Cheap if you already have a smartphone.

As you may be aware, there are a shed load of headtracking solutions out there. Some are expensive (TrackIR, I'm looking at you). Some are CONSTANTLY around the corner yet out of reach but could be the holy grail (Oculus rift). Some are very cheap but completely and utterly pants (FacetrackNoIR) and Some are a bit fiddly to build yourself but offer good results and can be bought prebuilt for a lot cheaper than TrackIR.


Worry no more.
There is a quick and easy solution if you have a smartphone.

Android:

Go to Google Play store and Download 'HeadTracker' https://play.google.com/store/apps/details?id=com.frozenbacon.headtracker
It's the Lawrence Simmons version, there are others that dont work.
Follow the onscreen instructions on your phone.
Make sure you go to the settings and enable 'Transmit in Background' which will allow it to work with the screen off. 

You'll also need software on your computer. I'm using OpenTrack.

https://github.com/opentrack/opentrack/ ... 2.3-rc21p7  Download link is at the bottom of the page.
You don't need to install, just extract to a folder of your choice and launch using the exe in the folder.

It really is easy to set up. 

iPhone:

Not a clue, go ask an iGenius or work it out yourself you trendy hipster


Results:

I'm very happy with it. Using just the pitch and yaw, disabled everything else. Having a play with the mapping sensitivity to get it right for me.
I've mounted the phone on my headset using an 'elastic band' made from the top of an old clean  sock. it lost its friend to the drier monster ages ago so is happy to have been found something useful to do other than catch sweat and dead toe skin.
Response seems very good and absolutely zero jitter which I have had with optical solutions. It doesnt wander noticeably. I went to the loo with it on my head and when I came back it was still good to go without having to hit the centre button (you'll need to set this in OpenTrack as well as 'toggle' to switch it on and off)

Another tip, When mounting your phone onto headset, it needs to be face(screen) side up, top nearest monitor and as level as possible.

Genius...

Hey, it works. 

Glad you found something that works, although I'm surprised by the accuracy you're getting.  From my experience of using both accelerometers and giros in mobiles, they prone to drifting.

What sort of battery life do you get?

All giros drift. It is just a basic fact you can not avoid, unless you want to stop the earth turning and moving around the sun. You see, giros want to stay in a fixed point in space but because the earth is moving , there is a percieved drift. In fact the giro isn't actually drifting but you are, along with the entire planet.

What I've taken as 'drift' in others statements is accuracy rather than actual drift. Ie the ability of the tracking to retain the relationship between your head position and the display (obviously taking into account a very small wander in a constant direction over time). Obviously it helps to have a 'center' button if playing for extended periods of time.

Battery life, honestly makes no noticeable difference as its not using any extra resources bar sending giro data over an already established wifi connection. 

I'm finding easier to fly in 1st person but it's just going to take a bit of getting used to and programming my use of the freelook key out of muscle memory.

Also to add. I wouldn't use the accelerometers in a mobile. They are nowhere near accurate enough. (I did Avionics in the RAF, inertial navigation was my thing).

The giros on the top end phones are good and handle 3dof (pitch yaw roll) very well. Just don't bother with a 6dof setup.

Just a little physics/engineering niggle here, but the main cause of gyro drift is actually due to friction in the bearings and environment of the flywheel (in the case of flywheel gyros, which to my understanding are still the predominant type in mobiles). Regardless, even with the accelerometers not being great, by comparing the output from the gyro with the accelerometers, you're able to create a far more accurate and stable measurement than with either alone.

</offtopic>

Its the wander that I was referring too as drift. Have done a lot of research around position sensors, including those in mobiles, which are really are not that good. We have to put Kalman filters on them to reduce jitter, but that does not stop the drift. Also the accuracy is very asymmetric, with the one axis far more inaccuracy that others. They're built into most VT headsets but are supplemented by optical tracking, to get the accuracy. The main advantage of the giros is the speed of update. You can get orientation information, at the 90-120 Hz required for the VR helmets, then update with the optical at a slower rate to improve the accuracy.

No mate. The main cause of drift is the earths rotation of aprox 15 degrees per hour. Obviously there are other variables involved such as relative position and direction to earths axis, position of the earth in orbit of the sun as well as friction, gimble error and measurement limitation/error. This is why inertial navigation systems are integrated with many other sub systems such as flux gates/valves found in the GMC, radio beacons on VOR and of course GPS.