The Hardware Hack That Makes 3D Modeling Intuitive

Traditional computer input devices, such as the keyboard and mouse, were not created for manipulating 3D digital environments. This means that if you are designing a 3D model, you will have to constantly shift your hand from keyboard to mouse, memorize countless keyboard shortcuts, and generally do lots of unintuitive things. This is all very cumbersome and it decreases productivity. It also hinders the flow of creativity.

David Liu was fed up with the status quo, so he built his own input device: a 3D trackball called Rotatrix that makes it simple and intuitive to navigate 3D environments. It’s heavily inspired by the SpaceMouse, but Liu believes that his design feels even more natural to use.

Rather than designing a device from scratch, Liu took a clever shortcut by modifying a commercially available high-end trackball, the Kensington SlimBlade Pro. This choice wasn’t arbitrary — the device already contains dual optical sensors and a large, weighted ball capable of detecting nuanced motion. While the stock hardware uses these sensors primarily for standard cursor movement and a twist-to-scroll feature, Liu realized they could be repurposed to capture full three-axis rotation data.

To unlock that potential, he opened the device and reverse-engineered the communication protocol of the sensors. The original controller, limited to basic human interface device outputs, was bypassed in favor of a custom microcontroller. This new controller intercepts and decodes raw sensor data in real time, allowing the system to track rotation across the X, Y, and Z axes. By comparing motion data from two different sensor positions, the firmware calculates complex rotational vectors — including twist — transforming the trackball into a true 3D input device.

But a complete 3D controller must also handle translation — moving objects or the camera through space. Liu addressed this by implementing a mode-switching system using the trackball’s existing buttons. In its default state, Rotatrix behaves like a normal mouse. When modifier keys such as Control or Shift are engaged, the same ball movements are remapped to perform panning and zooming operations. For example, twisting the ball controls depth (zoom), while lateral movements handle horizontal and vertical translation.

Integrating this custom hardware with professional 3D software proved to be a challenge. Standard drivers couldn’t cut it, so Liu developed deeper software integration that enables context-aware navigation. The system can detect the surface under the cursor and dynamically set a pivot point, ensuring smooth and predictable rotations without the disorienting drift common in many 3D tools.

The final result is a hybrid device that merges traditional 2D cursor control with full six-degree-of-freedom manipulation — plus two additional degrees for standard mouse input. Users can switch between modes without lifting their hand, creating a more fluid and immersive workflow.