Surplex

Surplex
Basic Info
VR/AR	Virtual Reality
Type	Full-body tracking accessory
Subtype	VR tracking shoes
Platform	SteamVR
Creator	Surplex
Developer	Surplex
Manufacturer	Surplex
Announcement Date	August 2022
Release Date	2023
Price	US$169 (Basic), US$199 (Pro) Kickstarter pricing
Website	https://www.kickstarter.com/projects/surplex/surplex-future-vr-tracking-shoes
Versions	Surplex (Basic), Surplex Pro
Requires	SteamVR-compatible PC VR headset, gaming PC
Predecessor	None
System
Operating System	SteamVR
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	Sensor-fusion (pressure sensors + IMU + deep-learning skeletal inference)
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
Update Rate	30 Hz (Basic), 60 Hz (Pro)
Latency	~30 ms
Audio
Audio	N/A
Microphone	N/A
Camera	N/A
Connectivity
Connectivity	Wireless to PC (Wi-Fi)
Ports	USB-C (charging)
WiFi	Yes
Power	Rechargeable battery
Battery Life	~6 hours (Basic), ~9 hours (Pro)
Device
Dimensions	Shoe form factor
Weight	Lightweight (figure not published)
Material	Footwear with embedded sensors
Headstrap	N/A
Haptics	N/A
Sensors	240 flexible pressure sensors per shoe (480 total) plus one 9-axis IMU per shoe
Input	Foot pressure and motion
Compliance	SteamVR compatible

Surplex is a Virtual Reality full-body tracking accessory that takes the form of a pair of shoes. Instead of relying on external Base Stations, cameras, or strap-on body trackers, Surplex embeds an array of flexible pressure sensors and an inertial measurement unit (IMU) in each shoe and uses a deep-learning algorithm to infer the wearer's full-body skeleton from how their feet move and press against the ground. The system is developed by the company Surplex, founded by Axl Chen (also rendered as Axl Chan in some early materials), and was first announced in August 2022 ahead of a Kickstarter crowdfunding campaign.

The product is designed for social and physically active VR applications where leg, hip, and torso movement add to immersion, such as VRChat, Beat Saber, Blade and Sorcery, and Neos VR. Because tracking is generated on the shoes themselves rather than by a fixed external rig, Surplex offers what the company calls 360-degree coverage with no fixed play boundary and no drift, communicating with the user's gaming PC wirelessly over Wi-Fi. Surplex was named a 2023 CES Innovation Awards Honoree in the Virtual and Augmented Reality category.

Background and development

Surplex was created by Axl Chen, a graduate student who studied at Parsons School of Design at The New School, where the project was credited to him as part of the Design and Technology class of 2023. According to The New School, Chen conceived the idea while studying abroad at Tsinghua University through a Parsons offsite program. As a member of the university's snowboard team, he had used wearable sensors to analyze and improve his athletic technique but found existing on-body sensor setups cumbersome, which motivated him to build a full-body tracking system integrated into footwear instead. Early team members named by the university included fashion-design graduate Yuedi Zhang alongside engineers and technical advisers. The work was also profiled by Columbia Engineering, which described Chen as a master's student developing VR full-body tracking shoes.

The company that commercialized the design, also called Surplex, was reported to be based in Shenzhen, China at launch. Chen is described as the founder and chief executive of Surplex, positioning the company around full-body tracking technology for gaming and professional sport. Founder Axl Chen summarized the design goal as removing the friction of conventional tracking, stating that the product was meant to deliver "true freedom for a fascinating new world" without "complicated setups, base stations, dongles, or straps."

How it works

Each Surplex shoe contains roughly 240 flexible pressure sensors built into the sole, for a total of about 480 sensors across the pair, together with a nine-axis IMU per shoe to capture orientation and angular motion. Reporting on the product identifies the IMU as a Bosch BNO085 nine-axis sensor. Rather than measuring the rest of the body directly, the system reads the changing pressure distribution under each foot and the IMU data and feeds them into a proprietary deep-learning model that reconstructs a 3D skeleton of the user. The team reported training the neural network on roughly 500,000 frames of motion data.

From this sensor fusion the shoes estimate the position and rotation of the user's feet, knees, waist, chest, and elbows. New Atlas reported a body-position accuracy of within about 5 cm (2 inches) and a latency of roughly 30 milliseconds, with the system supporting users weighing between 50 and 120 kg (110 to 265 lb). Because the tracking originates from the shoes and is sent to the PC over Wi-Fi, Surplex does not require the externally mounted Lighthouse base stations or camera arrays used by many SteamVR full-body setups, and the company claims it avoids the occlusion and drift problems those approaches can suffer.

Variants

Surplex launched in two tiers, a standard model and a higher-end Surplex Pro, which differ mainly in update rate and battery life. The Pro model is documented as offering 480 pressure sensors and two IMUs across the pair, a 60 Hz update rate, and up to nine hours of battery life.

Specification	Surplex (Basic)	Surplex Pro
Pressure sensors	240 per shoe (480 total)	240 per shoe (480 total)
IMU	9-axis per shoe	9-axis per shoe (BNO085)
Update rate	30 Hz	60 Hz
Battery life	~6 hours	~9 hours
Kickstarter price	US$169	US$199

Compatibility

Surplex is built for the SteamVR ecosystem and is described as working with SteamVR-compatible headsets, with the HTC Vive, Oculus Quest 2, and Valve Index cited as examples. The tracking data is delivered to the user's gaming PC wirelessly, so use is not confined to a single calibrated play area. On the software side the shoes are aimed at full-body tracking experiences and have been promoted as compatible with VRChat, Beat Saber, Blade and Sorcery, and Neos VR, among other titles. The company has also suggested applications beyond gaming, including 3D animation, film and game production, and motion analysis for athletic performance and rehabilitation.

Crowdfunding and release

Surplex ran a Kickstarter campaign for the shoes beginning in September 2022. The campaign set a funding goal of US$10,000 and ultimately raised US$61,598 from 302 backers, finishing in October 2022. Early-bird Kickstarter pledges were priced at US$169 for the standard model and US$199 for the Pro, described as about 25 percent below planned retail pricing. The product was subsequently presented as a 2023 release and continued to be offered through follow-on crowdfunding on Indiegogo.

Reception

Coverage of Surplex focused on its unconventional approach to full-body tracking, which sidesteps the external base stations and strap-on trackers common to existing solutions. New Atlas described it as tracking full body position via a pair of shoes and highlighted the lack of base stations and the wireless, room-independent operation. Inverse framed the device as an attempt to bring body-tracking shoes to virtual reality and noted that at the time of its preview the deep-learning algorithm was still being refined. The selection of Surplex as a 2023 CES Innovation Awards Honoree in the Virtual and Augmented Reality category gave the project additional visibility within the wider XR industry. Independent long-term hands-on reviews of retail units remain limited.

See also

• Cybershoes
• Vive Tracker
• Positional Tracking
• SteamVR
• VRChat