SlimeVR Unveils the Butterfly, a More Comfortable Take on the Nordic nRF-Powered VR Body Tracker

The full-body tracking virtual reality project SlimeVR is back with redesigned tracking hardware, promising a more comfortable and long-lasting design: the SlimeVR Butterfly Tracker.

"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," says SlimeVR's Eiren Rain. "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."

This isn't SlimeVR's first shot at a body-tracking device: back in 2021 the company opened a crowdfunding campaign for its original sensors, built around an Espressif ESP12-F ESP8266 module and delivering a 100Hz refresh rate over a claimed 15-hour battery life. A later update, the Smol Slime, moved to the Nordic nRF52840 to boost performance and increase battery life still further — and it's this latter redesign that serves as the basis for the new SlimeVR Butterfly.

The biggest change from the Smol Slime: a shift to a new two-part split design, with the two halves connected via a flexible hinge. This, its creators claim, reduces overall thickness to just 7mm (around 0.28") for improved comfort while allowing it to follow the body's contours — important, given you're to wear six of the things for complete full-body tracking.

Data from the on-board inertial measurement unit (IMU) are transmitted to the SlimeVR Server software using Enhanced Shockburst, with a custom antenna design provide a claimed 10m (around 33 feet) range. The internal 100mAh battery, meanwhile, is said to be good for a full 24 hours of playtime. The refresh rate is projected to be between 100Hz and 140Hz, yet to be finalized, and each tracker weighs less than 12g (around 0.4oz).

"SlimeVR is open hardware driven by open source software and is released under permissive MIT & Apache 2.0 licenses," Rain adds. "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."

Interested parties can sign up to be notified when the crowdfunding campaign goes live on the project's Crowd Supply page; design files and source code are available on the project's GitHub repository under the aforementioned open licenses.