SlimeVR Butterfly Trackers
Super comfortable IMU body-tracking for virtual reality, motion capture, and VTubing
This project is launching soon.
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This project is launching soon.
Based on the success and experience of SlimeVR Full-Body Trackers, SlimeVR Butterfly Trackers expand the limits of comfort and ease of use of body trackers for virtual reality, motion capture, streaming, and more.
Like the original version, these new SlimeVR Butterfly Trackers are open hardware sensors with open-source software that can track the movement of your body. They require no base station, can’t be occluded, last for days on a single charge, and are completely wireless. Now, with the brand-new, unique, ultra-light split design inspired by butterflies, they’re less than 7 mm thick and weigh less than 12 grams, making them the most comfortable solution for full-body tracking on the market today.
Each SlimeVR Tracker tracks its own absolute rotation using an IMU (Inertial Measurement Unit). It sends the data wirelessly to SlimeVR Server running on your PC or smartphone. The SlimeVR Server combines the data from multiple trackers and your body proportions to calculate the position of your body parts using your headset as a reference point. They don’t require base stations or cameras, so they can’t be occluded, and can be used under a blanket, or worn under clothing, or in a small space!
SlimeVR Server is the open-source software at the heart of it. Developed over 4 years by our team, with contributions from over 50 community members and dozens of translators! Compatible with a lot of ecosystems, like SteamVR, OSC, VMC, BVH, and OpenXR, it lets you use SlimeVR however you want - for gaming, streaming, motion capture, and more!
SlimeVR Butterfly Trackers are based on Smol Slime, SlimeVR trackers that use Nordic’s nRF chips to reduce power consumption compared to the original Slimes, which used Espressif chips and Wi-Fi. Smol Slimes have been in development by our team and community for years now, but with Butterfly Trackers, we’re pushing the format to its limits.
The most critical parameter for the comfort of body trackers is their thickness. By placing the PCB and battery of the tracker side by side, we achieve a thickness of less than 7 mm without compromising the enclosure’s durability.
To make it even better, the two halves of the tracker are connected by a durable yet flexible band, which helps them bend and better contour the body for maximum comfort. Both of these changes make the trackers almost unnoticeable when worn, even when lying on them!
Smol Slime and SlimeVR Butterfly Trackers, unlike the original SlimeVR, don’t use Wi-Fi; instead, they utilize Enhanced ShockBurst (ESB), a technology similar to Bluetooth but with fewer limitations. They require their own dongle to connect them to a PC. Most of the community projects based on Smol Slime suffer from poor signal strength and short range. For Butterfly Trackers, we are using a custom PCB with a professionally tuned antenna specifically designed for small wearable devices so that we can achieve distances of over 10 meters from the dongle, no problem. Stay tuned for the in-depth testing and final range numbers before the launch.
Both the microcontroller and IMU of the Butterfly Tracker are very low-powered and can last over 24 hours of play time on one battery charge with a tiny 100 mAh battery! When combined with the deep sleep feature, you would only need to charge them about once a week or less if you play a few hours a day.
When you do need to charge them, we now offer a very convenient charging station! It’s sold separately, so if you prefer saving a bit of money, charging them with any USB Type-C cable is also possible.
Because Butterfly Trackers don’t use Wi-Fi, fiddling with your router is no longer required! Just plug the dongle into your PC: they’ll be instantly recognized by SlimeVR Server, no drivers or settings required!
Butterfly Trackers have a hooked backing from the hook-and-loop system (commonly called Velcro), and a set of straps is included in each set. This design also allows it to be attached to any Velcro-like fabric, providing a lot of flexibility and creativity for mounting. Feel free to experiment with other ways of wearing them, such as custom clothing with loops for easy attachment of trackers, adhesive silicone backing, belt clips, and any other ideas you can think of. Don’t be afraid to get creative! They can also be transformed into a single unit if that’s what you prefer. Some of the tools for these options will be included in the set, while others will be sold separately. Stay tuned!
SlimeVR is broadly supported by popular VR software, including:
And many more as we grow!
* Not all specs are finalized at this stage, stay tuned for more info before the campaign launch!
| Butterfly Trackers | SlimeVR v1.2 | Vive | Tundra | Amethyst | HaritoraX 2 | mocopi | |
|---|---|---|---|---|---|---|---|
| Developer | SlimeVR | SlimeVR | HTC | Tundra | K2VR Team | Shiftall | Sony |
| Form factor | 6x 12 g trackers | 5x 50 g trackers | 3x 75 g trackers | 3x 50 g trackers | Central camera | 6x 17g trackers | 6x 8g trackers |
| Battery Life | 24+ h² | 20 h | 7.5 h | 7 h | ∞ | 50 h | 10 h |
| Base station | No (own 2.4Ghz dongle) | No (Wi-Fi) | SteamVR Lighthouse | SteamVR Lighthouse | Kinect | No (Bluetooth or own 2.4Ghz dongle) | No (Bluetooth) |
| Prone to occlusion | No | No | Yes | Yes | Yes | No | No |
| Coverage | 360° | 360° | 360° | 360° | 360° | 360° | 360° |
| Precision | 1-10 cm ¹ | 1-10 cm ¹ | < 1 mm | < 1 mm | 1-10 cm | 1-10 cm ¹ | 1-20 cm |
| Latency | < 15 ms² | ~15 ms | ~15 ms | ~15 ms | ~20 ms | ~15 ms (with dongle), >15 ms (Bluetooth) | 50+ ms |
| Update rate | 100-140 Hz² | 100 Hz | 90-144 Hz | 90-144 Hz | 30 Hz | 50-100 Hz | 50 Hz |
| Range | > 10 m² | Wi-Fi coverage | 10 m | 10 m | 2-4 m | Bluetooth / dongle coverage | Bluetooth coverage |
| Can track any object | No | No | Yes | Yes | No | No | No |
| Open Source | SW + HW | SW + HW | No | No | SW | No | No |
¹ The precision of SlimeVR, HaritoraX & mocopi tracking technology depends on your setup, on the plane used for measurement, and on how your back bends.
² Not all specs are finalized at this stage; stay tuned for more info before the campaign launch!
Since our original campaign began in 2021, a whole industry of IMU-based VR body trackers has emerged and matured, with many manufacturers offering their own solutions, as well as dozens of third-party SlimeVR-compatible trackers. Despite that, we believe that SlimeVR is still the leader in the space. Here are a few things that we have that others don’t:
Butterfly Trackers add even more unique and important features:
SlimeVR is open hardware driven by open source software and is released under permissive MIT & Apache 2.0 licenses. This open design empowers the VR community to expand on the SlimeVR ecosystem, create new devices, add compatibility with new software, and improve upon all aspects of the project.
For our part, we are focused on helping that community expand SlimeVR infrastructure by adding support for various devices, protocols, and features. We are part of an active DIY community, members of which build their own SlimeVR trackers, help others get into DIY electronics, contribute to our documentation, and develop hardware with different features and at different price points.
Our open-source software and firmware are in our GitHub repository. We have guides and schematics for easy DIY, and our community is constantly working to make them better, more accessible, and compatible with a wide range of hardware and tools.
More specifically, our documentation is here, and our GitHub repository contains:
Stay tuned for the official hardware design to be released after it’s finalized. In the meantime, check the community designs if you want to build a set yourself.
Join our community on Discord to meet other VR hackers or to chat about SlimeVR. You can also find us on YouTube. And, if you have a question for our team, you can reach out using the Ask a technical question link below.
Check our site for other links and more information.
SlimeVR includes a 2-year manufacturer’s warranty. The warranty starts on the day you receive your products. For any warranty-related questions and claims, visit our Contact Page.
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Do you want more updates? Follow us on the many platforms where we post regularly about this and our other projects development and fulfillment as well as other cool things:
· slimevr.dev · SlimeVR@mastodon.social · officialslimevr · SlimeVR · slimevr.dev
A small company enthusiastically pursuing the goal of bringing accessible VR to a wide audience.
