Full Body Tracking

What is full body tracking?

Full body tracking (also known as FBT) refers to allowing tracking of more than the hands and head in VR, typically referring to the legs and hips of a user. This is typically done using trackers that are worn by the user.

What is full body tracking used for?

Full body tracking, when referred to tracking of the lower body, allows for full pose estimation which is very fun for social VR settings.

You will see this tech used by people who dance in VR or do other active activities, but also by people who spend most of their time sitting, as it just improves immersion for oneself as well.

Keep in mind a majority of VR applications do not make use of FBT, so be sure to check if the software you are using supports FBT before spending money on additional hardware!

So lets say you are interested in acquiring FBT. For the sake of discussion, lets divide types of FBT into 3 general categories:

• Wearable Trackers
• Fake / emulated FBT
• External cameras that track your body

Wearable Trackers

These are trackers that you strap on to yourself. Usually this consists of needing to wear trackers on your feet and hips, though some solutions require more. This solution generally costs the most money (depending on the implementation you choose) but will give the best results, and thus is the most common form.

A lot of these trackers will need some form of straps to have them actually be worn. You can find FBT straps with google searches on store-fronts like amazon, but I personally really enjoy the ones made by EOZ.

Individual trackers are generally separated in groups based on their tracking methodology. It may be worth a read here if you want to know the details.

SteamVR based tracking

Remember, for these trackers you need to have base stations! In addition, each tracker needs its own Watchmen USB dongle to connect, read more here under the dongles section.

For SteamVR based FBT tracking, for tracking your lower body (legs and hips), you will need 3 trackers + straps in most implementations, such as with VRChat. You can mix and match between SteamVR trackers freely, 

Vive Tracker 2.0

These can be identified as being larger with a flatter bottom, and have a blue triangle. (Beware the trackers with the same shape that have a grey triangle, those are Vive 1.0 trackers and only work on 1.0 base stations while the blue Vive 2.0 trackers can use 1.0 or 2.0 base stations). 

These trackers are among the heaviest of the wearable trackers, yet also tend to have the worst battery lives, often only lasting 2-4 hours. You can get straps with battery extenders for these but that just makes things heavier. In addition, their firmware is a bit funky which sometimes makes them annoying to power on and connect. That being said, they still track very well and are functional, so if you can grab these used for a good deal they may be worth it to those on a budget (you can often find these used for around 50 dollars or so, just be wary about getting watchmen dongles too!)

Vive Tracker 3.0

These can be identified compared to 2.0 trackers as being smaller, lighter, and looking very triangular head on, and have a dark gray logo. Like the 2.0 trackers they work on either 1.0 or 2.0 base stations. However, their inner workings have improved such that they have a significantly higher battery life of over 7 hours, and are much lighter as well. Furthermore, their firmware doesn't have as many quirks about turning on and off like the 2.0 trackers, and they still track great. Of the SteamVR tracked trackers, these generally track the very best are the preferred trackers by many people, and is the best tracker to use for continuous calibration. These can be purchased new for 130 dollars but can often be found much cheaper used as well.

Tundra tracker

Of the common SteamVR trackers, this is the smallest and most compact one. Unlike the Vive trackers, they are distinctly square witha  single "rib" extruding diagonally from the center. Like the Vive 3.0 tracker, they have a 7+ hour playtime and also power on and off without much fuss. They also tend to be sold a bit cheaper new compared to the Vive 3.0. The one downside is due to their smaller surface area, they tend to suffer some tracking jitter (as in they "wiggle" a bit) compared to the Vive trackers. Generally, this still good enough for general full body tracking for most people, although this can cause issues with continuous calibration and thus is not recommended for that purpose.

IMU based tracking

Pico Motion Trackers

Pico motion trackers are IMU based trackers you can wear on your legs for FBT. What makes these unique compared to other IMU based solutions is that one can only use the on newer Pico headsets, and they they use IR for calibration using the headset itself, making them very easy and fast to setup. Most kits come with 2 trackers, which while technically work, you would likely want at least 3 (a third for your waist) for reasonably accurate IK for FBT. The devices themselves are generally pretty accurate in their tracking, although they do drift eventually like all IMUs, necessitating occasional calibration. However, due to Pico using IR to locate them, this process is extremely fast. They have a battery life of over 20 hours per charge.

Note that to use them for PCVR, the only streamer app that currently supports streaming them is Pico's own connection software. Currently you cannot use a solution such as SteamLink or Virtual Desktop.

Slime VR Trackers

SlimeVR are unique on this list as they are open source, therefore various manufacturers may build them differently with various shells. This means you can also build these trackers yourself for very cheap (though this takes some effort on your part). They generally track pretty well for IMU trackers, though this depends on the IMU sensor of your specific unit (some are better than others, beware as suspiciously cheap SlimeVR trackers may cheap out here). Due to variances that can exist between builds, it may be best to check their website for more specific information.

Also note some other IMU trackers can be set to use SlimeVRs algorithms and systems. A notable case would be Sony's Mocopii.

Inside-Out Camera Tracking

Vive Ultimate Tracker

This tracker, unlike HTC's other Vive trackers, does not use base stations. Instead, it uses cameras to track via VSlam, such as how Quest headsets track themselves. This additional processing requirement means these devices are quite expensive, and have poor battery life of only a few hours. Also unlike the SteamVR based Vive trackers, they do not connect via watchmen dongles, but rather their own specific dongles. BE SURE NOT TO MIX THIS UP WHEN ORDERING! Generally speaking, outside of some unique use cases, these trackers are not regarded as having particularly great tracking, which is a problem since they tend to be the most expensive option as well.

Fake / Emulated FBT

On the much cheaper end of the budget spectrum, instead of purchasing hardware to do FBT, we can use software to simulate what FBT would be like. Obviously this isnt nearly as good as having proper FBT tracking, but this can be appealing to those still on a budget and can be argued to be "better than nothing".

Standable

GogoLoco

External Cameras Tracking Your Body

This is generally not common anymore, but is mentioned here anyways. Generally this tracking type limits you to the space you can play or can only track certain regions, depending on the implementation.

Virtual Desktop Upper Body Tracking

Virtual Desktop on the Quest 3 is capable of tracking your shoulders for use in games like VR for slightly improved upper body FBT.

Kinect

This method really isn't recommended for practical FBT use

Sources and reviews