James Brown's Volumetric Displays Learn a New Trick: Tracking Where the Viewer Is
The ability to point towards a linked Bluetooth gamepad makes Brown's semi-spherical displays more usable for gaming.
Maker James Brown has added a new trick to his homebrew volumetric display technology: the ability to track the position of the viewer by monitoring the signal strength to a Bluetooth gamepad, taking advantage of a Raspberry Pi spinning at high speeds.
Brown has been working on his impressive displays for some time, showing off an early variant — which used 3D-printed lenticular lenses and collimators, later dropped for simply spinning plain HUB75 RGB LED matrices at somewhat worrying speeds — back in October 2023. The current generation sees a Raspberry Pi single-board computer used to control the boards, spinning round and round to deliver the 3D effect using persistence of vision (POV).
The fact the Raspberry Pi is spinning just like the LED matrix to which it's connected is the secret to Brown's latest breakthrough. "This nifty hack uses the fact that everything is spinning, including the Bluetooth antenna," he explains. "It creates a map of the signal strength to any connected controllers and points to where it's strongest."
Given that the semi-spherical displays have no concept of a "front," that trick is key to making them usable as a gaming display rather than a piece of art: by tracking a Bluetooth game controller, in James' experiments an Xbox pad, the display can orient itself so that the "front" is wherever the player happens to be — and the player can even move around the display and have it update with their current location automatically.
In Brown's demo video, the tracking is slightly lagged and a little glitchy — though the fact it works at all, given it's based on sampling signal strength at a high rate while the antenna spins like a top, is nothing short of remarkable. Asked whether it will be possible to stabilize or filter the signal enough to improve the performance, Brown says "I expect so."
As always, the latest project updates are published to Brown's Mastodon account; brown has also released a bill of materials, 3D print files, and the source code for those looking to experiment with the volumetric displays themselves.