Surplex Pro

Surplex Pro
Basic Info
VR/AR	Virtual Reality
Type	Full-body tracking system
Subtype	VR tracking shoes
Platform	SteamVR
Creator	Axl Chen
Developer	Surplex
Manufacturer	Surplex
Announcement Date	August 2022
Release Date	2023
Price	US$199 (Kickstarter pledge, pair)
Website	https://www.surplex.io
Versions	Surplex Pro, Surplex Basic
Requires	Gaming PC, SteamVR-compatible headset
Predecessor	None
Successor	None
System
Operating System	N/A
GPU	N/A
Storage
Storage	N/A
Memory	N/A
SD Card Slot	No
Display
Display	N/A
Resolution	N/A
Refresh Rate	N/A
Image
Field of View	N/A
Horizontal FoV	N/A
Vertical FoV	N/A
Optics
Optics	N/A
Ocularity	N/A
IPD Range	N/A
Adjustable Diopter	N/A
Passthrough	N/A
Tracking
Tracking	Pressure-sensor and IMU based, markerless (no base stations)
Base Stations	Not required
Eye Tracking	N/A
Face Tracking	N/A
Hand Tracking	N/A
Body Tracking	Yes (feet, knees, waist, chest, elbows)
Rotational Tracking	Yes
Positional Tracking	Yes
Audio
Audio	N/A
Microphone	N/A
Camera	None
Connectivity
Connectivity	Wi-Fi (to gaming PC)
Ports	USB-C (charging)
WiFi	Yes
Power	Rechargeable battery
Battery Life	Up to 9 hours
Device
Dimensions	Footwear form factor
Material	Textile footwear with embedded sensors
Headstrap	N/A
Haptics	N/A
Sensors	240 flexible pressure sensors per shoe (480 total); one 9-axis IMU per shoe
Input	Body motion (full-body tracking)
Compliance	SteamVR compatible

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The Surplex Pro is the higher-specification model of the Surplex virtual reality full-body tracking system, a pair of sensor-equipped shoes that estimate a user's whole-body pose for VR without external cameras, base stations, or body straps. Created by designer Axl Chen, the system places hundreds of flexible pressure sensors in each insole and combines their readings with an inertial measurement unit (IMU) and a deep-learning algorithm to infer the position and rotation of the wearer's feet, knees, waist, chest, and elbows. Surplex is designed to work with any SteamVR-compatible headset and communicates wirelessly with a gaming PC over Wi-Fi, allowing free-roaming movement. The Surplex Pro differs from the cheaper Surplex Basic chiefly in battery life and tracking update rate: the Pro offers up to nine hours per charge and a 60 Hz update rate, against six hours and 30 Hz for the Basic.

The project was funded on Kickstarter in 2022, where the Pro was offered for a pledge of US$199, and the company was named a CES 2023 Innovation Awards honoree. Surplex positions the shoes as an alternative to tracker-based solutions such as the Vive Tracker, which typically require SteamVR base stations or additional straps.

Development

Surplex was created by Axl Chen, a graduate of the Design and Technology program at Parsons School of Design (class of 2023). Chen, who founded the company and serves as its CEO, set out to make body tracking that felt as light and unobtrusive as ordinary footwear, avoiding the cameras, base stations, and strap-mounted trackers used by earlier consumer full-body tracking setups. To turn raw sensor data into a moving skeleton, the team trained a neural network on roughly 500,000 frames of human-motion data, pairing the pressure readings under each foot with IMU output to estimate joint angles across the body.

Surplex announced the product in August 2022 and ran a Kickstarter campaign from September 6 to October 21, 2022. The campaign sought US$10,000 and ultimately raised US$61,598 from 302 backers, reaching roughly 615 percent of its goal. Kickstarter pledges were US$169 for a pair of the Basic model and US$199 for a pair of the Pro, prices the company described as about 25 percent below the planned retail price. The shoes were also recognized as a CES 2023 Innovation Awards honoree.

Design and technology

Each Surplex shoe contains 240 flexible pressure sensors built into the insole, for a total of 480 sensors across a pair, plus a 9-axis IMU per shoe. As the wearer walks, runs, stands, or shifts their upper body, the distribution of pressure under the feet changes in characteristic ways; Surplex's deep-learning model interprets these patterns, together with the IMU's orientation data, to reconstruct the position and rotation of the feet, knees, waist, chest, and elbows in real time. Because the approach is based on what is happening at the feet rather than on line-of-sight to external sensors, the company describes it as offering 360-degree coverage with no blind spots and no positional drift.

The system is rated as accurate to within about 5 cm (2 in) of true body position, with end-to-end latency of roughly 30 milliseconds. The shoes are designed to fit users weighing approximately 50 to 120 kg (110 to 265 lb). Surplex communicates with the user's gaming PC over Wi-Fi rather than a wired tether, so the wearer is not confined to a precisely defined tracked volume and can move more freely than with base-station systems. The shoes are rechargeable; the Pro is rated for up to nine hours of use per charge.

Models

Surplex was offered in two variants. The differences between them are summarized below.

Specification	Surplex Basic	Surplex Pro
Battery life	Up to 6 hours	Up to 9 hours
Tracking update rate	30 Hz	60 Hz
Pressure sensors	240 per shoe (480 total)	240 per shoe (480 total)
IMU	One 9-axis IMU per shoe	One 9-axis IMU per shoe
Tracked body parts	Feet, knees, waist, chest, elbows	Feet, knees, waist, chest, elbows
Connectivity	Wi-Fi to gaming PC	Wi-Fi to gaming PC
Kickstarter pledge (pair)	US$169	US$199

Aside from the higher battery life and the faster 60 Hz update rate, the Pro shares the Basic model's sensing hardware, accuracy, and compatibility.

Compatibility and software

Surplex is presented as a platform-agnostic accessory that works with all SteamVR-compatible headsets, exposing its tracked points to the SteamVR runtime in the same way other full-body tracking peripherals do. The company has cited support for popular full-body tracking titles and social platforms including VRChat, Blade and Sorcery, Beat Saber, and Neos VR. Surplex has also said it was in discussions with studios behind fitness and sports applications such as VRWorkout, Planet Theta, and Tennis Esports.

Beyond gaming and social VR, the company has suggested wider applications for the underlying motion-capture technology, including character animation for film and games and movement analysis for athletic performance and rehabilitation.

Reception

Coverage framed Surplex as a notably compact take on consumer full-body tracking, since it removes the cameras, base stations, and waist or limb straps associated with rival systems and instead concentrates the sensing in a single pair of shoes. The strong Kickstarter response, more than six times the funding goal, was taken as a sign of demand for lighter-weight tracking among VR enthusiasts. The company's selection as a CES 2023 Innovation Awards honoree brought additional attention to the design. As a crowdfunded hardware product, independent long-term hands-on reviews of shipped units were limited, and as with other crowdfunded peripherals real-world accuracy and durability depend on final production hardware.

See also

• Full-body tracking
• HTC Vive Tracker 3
• SlimeVR
• Tundra Tracker
• SteamVR
• Inertial Measurement Unit