Intro

This is a simple app which makes it possible to use your Apple device as a fairly low latency and high accuracy head tracker by mounting it to your head.

The app will wirelessly send its attitude, from the built-in accelerometer and magnetometer, to a computer running Opentrack.

Screenshots and video

Here's a demo video.

Note: When you first try it, you'll probably notice higher latency than shown in the video. This is because I turned down the filtering. You should play around with different filters/settings in Opentrack until you find a balance between smoothness and low latency.

Pros and cons of using this method for facetracking

• Lower latency and higher accuracy compared to visual (no-IR) tracking solutions.
• It's free. (Assuming you already own an Apple device)
• You need to strap your phone to your head.
• This can only track your head's rotation, no translation.

I don't know how this compares to IR tracking as I can't test it myself. I'd assume the accuracy is comparable and the latency is slightly higher. I'll update this if someone let's me know.

Requirements

• An iPhone, iPod Touch or iPad*
• iOS 13.0+
• Opentrack
• A way to mount your device to your head

*The app works on iPad in case you want to test it, but I wouldn't recommend actually mounting an iPad to your head.

Installation

This app is not available on the App Store, as I'm not going to pay 99 Euros/year for an Apple developer account. This means installing isn't as simple as pressing a button, instead you'll have to use a 3rd party tool to install unsigned apps to your device by signing them with your own Apple ID.

I've tested Sideloadly for Windows which worked fine.

Click to unfold installation guide ...

1. Install iTunes (64bit/32bit) if you haven't got it yet.
2. Install Sideloadly.
3. Connect your device to your computer.
4. Start Sideloadly, you should see a bunch of letters/numbers in the 'Device' dropdown if your device is plugged in.
5. Go to releases, download the .IPA file and drag it to the Sideloadly window.
6. Enter your Apple ID you'll be using to sign the app.
   If you don't want to enter your own Apple ID into a random tool, you can use 'no2fa.cecemel@gmail.com'. This is an Apple ID without two-factor authentication (2FA) that I made specifically for this purpose. Send me a message on Discord (Cedricdb#6035) to get the password.
   
   
7. Click Start and enter the password for the Apple ID.
   • If you're using an account with 2FA, you'll get a message on an Apple device. Confirm it, it'll give you a 6-digit code that you'll need to enter in Sideloadly.
8. Wait a few seconds. If 'Done.' appears, the app is installed. I had to reboot my iPhone before it showed up on the homescreen.
9. Before you're able to start the app, you'll need to 'Trust' the Apple ID you used to sign the app. Go to Settings --> General on your device and scroll down.
   
   
10. Go to 'Device Management', press the email address you entered previously, press the 'Trust ...' button and confirm.
    
    
11. That's it, you should now be able to run the app.

Usage

Using the app is pretty simple.

1. Start Opentrack on your computer and the app on your mobile device.
2. In Opentrack, under input, select 'UDP over network'.
3. Click the hammer icon net to it and make sure the port matches the port in the app (default is 4242).
4. Select a desired output. ('freetrack 2.0 Enhanced' for most games)
5. Go to 'Options' --> 'Output' and invert yaw and roll.
   • Make sure you also set a key for centering the view under 'Shortcuts'. (I'm using the home key)
6. Press 'Start' in Opentrack.
7. In the app, enter your local ip address, set a rate and press the switch to enable. You should see Opentrack's icon move along with your phone.
   • When using little filtering, you should probably set the rate to 66 or 100Hz. With heavier filtering, you can go as low as 30Hz without noticing a difference. This will save a little battery.
8. Mount your device to your head. The orientation doesn't matter, you can put it horizontally on top of your head, vertically by your ear, ... The easiest is probably to strap it to your headphones using a rubber band.
9. When everything's set up, look at the center of your monitor and press the center key.
10. The last step is to adjust your curves under 'Mapping'. Here are mine, as a starting point.

Note

This is my first time writing an iOS app, using Xcode and using Git(Hub). The code writen will certainly not be ideal, but it runs pretty efficiently and doesn't seem to contain bugs. Bug reports, improvements, feature requests, ... are always welcome.

Also, feel free to suggest an app icon.