VR Full Body Tracking Guide: Pros and Cons of Tracker Technologies

When we talk about Virtual Reality (VR), having a good VR headset is important, but why stop at just moving and tracking your hands? With the help of motion trackers, attaching these additional trackers to your joints or other objects can capture real-world movements in real-time and accurately map them into the virtual environment. This allows you to move from head to toe, taking the immersive experience to the next level! VR tracking technology plays an indispensable role in various fields such as VR social interaction, VR gaming, medical rehabilitation, and professional training.

VR tracking technology perfectly unifies your body with your Avatar.

Base Station Tracking Technology: The Choice for High-Precision

• Pros: High precision, high stability
• Cons: Complicated setup, lower mobility

To achieve precise location tracking in virtual space, base station systems (such as the Lighthouse technology used by SteamVR and HTC VIVE Base Station) play a crucial role. These base stations act like an indoor satellite navigation system, using emitted light beams or wireless signals to locate trackers and VR headsets in the tracked space. This allows every movement and subtle action to be precisely detected, mapped, and tracked.

The advantage of this technology is its high precision, making it suitable for pro-level players or applications that require high accuracy, such as detailed motion capture or professional training simulations. The downside is that setting up base stations can be a bit of a hassle, with many variables and limitations to consider. In addition to having enough space to set up these base stations, you also need to be mindful of the layout of the space and potential issues with light reflection. Moreover, if you want to play VR in another room, you'll have to go through these tedious setup procedures again.

The setup process of using base station tracking is more complex, but correspondingly, the accuracy is higher. (Source: HTC VIVE)

IMU Technology: The Combination of Portability and Flexibility

• Pros: Portable and lightweight, no need for base stations, lower cost
• Cons: Lower precision, susceptible to environmental magnetic fields

If you say, "I just want to 'come alive' in the virtual world" and don't want all the hassle of doing a setup, then a lightweight and portable IMU tracker might be a good choice. For example, Sony's popular Mocopi tracker uses IMU technology and is aimed at general consumers.

IMU (Inertial Measurement Unit) is a device built into the tracker, typically using a three-axis gyroscope and accelerometers in three directions to measure and calculate the object's relative motion. These sensors provide data about the object's velocity, orientation, and acceleration, thereby inferring changes in the object's position. The benefit of IMU technology is that users can move freely without the need for any base stations to track their movements. However, this system is not perfect; IMU tracking can only provide motion data relative to the starting position, and it does not know the object's absolute position in space. Therefore, without external reference points and without strong algorithms for calibration, IMU tracking can easily and quickly accumulate errors over time, leading to “drift”, latency, and other serious tracking issues.

The Emergence of Self-Tracking Trackers: A New Era of Tracking Technology

• Pros: Portable and lightweight, no need for base stations, high precision
• Cons: Lower occlusion resistance, requires sufficient lighting

In response to the limitations of the two technologies mentioned above, self-tracking, which is primarily based on Computer Vision (CV) with IMU as a supplement, has emerged. This was first seen in HTC VIVE's VIVE Ultimate Tracker, released in 2023. This technology not only provides relative positioning data from IMU technology but also senses the space through two wide-angle cameras on the tracker (similar to the cameras on VR headsets), and then uses AI technology to calculate the precise absolute position in real-time.

The key is that up to five VIVE Ultimate Trackers can be supported simultaneously, requiring only a wireless receiver the size of a USB receiver to connect. The self-tracking tracker not only avoids the common errors of IMU but also does not require any base stations to be set up at home, providing users with a more convenient and accurate tracking method, making VR full-body tracking both intuitive and reliable.

Take a look at the two cameras on the VIVE Ultimate Tracker. (Source: HTC VIVE)

Introduction to Common VR Trackers

VIVE Tracker 3.0

VIVE Tracker 3.0 is a tracking product launched by HTC in 2021 to enhance the user’s VR experience. This tracker uses SteamVR tracking technology, which can accurately track the position of users and objects, and supports full-body and object tracking functions. It has a built-in battery and wireless module, which can be used continuously for up to 7 hours, and can be connected to other objects such as guns, rackets, keyboards, etc., through accessories. It is also widely used in fields such as virtual production.

After more than three years of user feedback and continuous improvement on the previous generation product Tracker 2.0, HTC launched the VIVE Tracker 3.0, which is smaller in size, lighter in weight (75 grams), and has stronger battery life, while maintaining accuracy and comfort.

Since its launch, the VIVE Tracker 3.0 has won unanimous praise from users for its precise tracking effect, 7.5 hours of battery life, and convenient usage. This tracker, with its outstanding performance and wide applicability, has not only become the ideal choice for VR enthusiasts but has also shone brightly in the field of motion capture. Traditional motion capture systems are usually expensive and complex to set up, requiring professional studios and a lot of equipment. However, the VIVE Tracker 3.0 has completely disrupted the motion capture industry, providing a more economical and portable solution.

Tundra Tracker

The Tundra Tracker was developed by Tundra Labs and launched a crowdfunding campaign in 2021, ultimately raising more than double the original funding goal. Tundra Labs aimed to create a high-performance tracker that could compete with the HTC VIVE Tracker but was lighter and cheaper. The Tundra Tracker weighs no more than 50 grams (depending on the base) and has a battery life of up to 7 hours. Like the VIVE Tracker, the Tundra Tracker also requires the setup of base stations.

However, due to the global shortage of components, Tundra Labs had to adjust the price of its products. For example, a set of three trackers that sold for $300 during the Kickstarter campaign is now priced at $378 on the official website, and the set is out of stock, with only individual trackers available for purchase. Despite the challenges, the launch of the Tundra Tracker has brought a lightweight and alternative option to the VR market.

Sony Mocopi

Sony Mocopi is a wireless VR tracking device specifically launched for VTubers and content creators. Users only need to install a dedicated app on their smartphone and wear six trackers, each weighing only 8 grams, on various parts of the body such as the head, wrists, ankles, and hips, to perform full-body tracking. These trackers collect motion data through the app, making it easy for users to record videos or import customized virtual characters.

Users generally find that Mocopi's performance in basic motion capture is acceptable. Although its precision is not comparable to higher-spec tracking devices, considering its relatively low price, Mocopi is especially suitable for entry-level creators and VTubers.

SlimeVR

SlimeVR, a full-body VR tracking device developed by the open-source community, was successfully launched through a crowdfunding platform in 2021. This device uses IMU technology for tracking and does not rely on base stations or other external devices. The basic SlimeVR kit includes five trackers, placed on the thighs, ankles, and chest, to capture lower body movements.

Most user reviews indicate that SlimeVR's tracking precision is not on par with the VIVE Tracker, and frequent calibration may be needed during use, especially when making large movements. Despite this, due to SlimeVR's convenience, high compatibility, and price advantage, many users consider SlimeVR to be a high-value full-body tracking option.

HaritoraX Wireless

Shiftall's HaritoraX Wireless, launched in 2023, is an IMU-based VR tracker that is extremely lightweight (17 grams) and has a long battery life of up to 20 hours. Compared to the previous generation HaritoraX 1.1, the biggest improvement of this device is that the new trackers are completely wireless, providing greater freedom for users engaged in activities such as dancing.

The basic HaritoraX Wireless kit supports 6-point tracking (chest, hips, knees, ankles), and additional trackers can be added to expand to 11 total tracking points. Moreover, it is compatible with various VR applications, such as VRChat and NeosVR, making it an ideal full-body tracking choice for VR enthusiasts.

VIVE VIVE Ultimate Tracker

The VIVE Ultimate Tracker can achieve 'self-tracking' without the need for external base stations or devices. It vividly and realistically brings the user's movements into the virtual and mixed reality worlds, thereby providing a more free and realistic interactive experience. In addition to being compatible with HTC VIVE standalone devices such as VIVE Focus Vision, VIVE XR Elite and VIVE Focus 3, VIVE also promises future support for PC VR devices based on OpenXR and SteamVR.

The VIVE Ultimate Tracker uses 6DoF inside-out technology, accurately tracking objects in 3D space with two wide-angle cameras. In addition to being worn on the body for full-body motion tracking, the VIVE Ultimate Tracker is also very suitable for tracking various objects. It uses a standard 1/4"-20 UNC threaded mount, which helps with quick installation and removal, and can be easily attached to various objects; HTC has also publicly released the 3D CAD files of the VIVE Ultimate Tracker, allowing users to design and manufacture mounts or bases that meet specific needs.

The VIVE Ultimate Tracker not only achieves a major breakthrough in portable positional tracking technology but also brings new possibilities to the XR ecosystem, especially for users seeking more realistic and immersive experiences, this is an innovative product worth paying attention to.

Comparison of Common VR Trackers

Conclusion

In this guide to VR full-body tracking, we have delved into the diversity of VR tracking technologies and their key role in enhancing virtual reality experiences. In summary, choosing the right tracking technology and equipment depends on individual needs, budget, and the level of experience desired. Whether for industrial applications, content creators, or users who want to enjoy VR gaming and social interaction, understanding the characteristics of these tracking technologies and comparing different trackers is crucial to selecting the most suitable equipment for oneself. With the continuous advancement of technology, we look forward to more innovative tracking methods that will make VR experiences even more vivid and fun.