Development Blog

It was time to build a tracked motion controller, and it started with my concept of Caliper, a mechanical measuring device.

Before getting deep into the design, I wanted to explore different options; it’s important to use practical modelling to quickly work through different ideas.

Many contemporary VR motion controllers could be simply described as “Banana with half-apple” in terms of form factor.

Banana being the held controller body

Half-apple being the finger input face
Index controller body
Fun modelling with foam, recreating Index controller body

After having a look at the current form factor, I wondered if there was there a better solution?

Why not try something different as well, perhaps a gun grip?

Building some working models would familiarise myself with controller development, before moving onto Caliper itself…

Early Sketchwork
5th Generation Analog mini-stick module with replaceable thumbcover
Foam wand mock-up with joystick module
Cutdown controller concept
Examining Index controller with trackpad ignored in favour of joystick on central axis
Analog mini-stick shown next to Index controller for scale
Classic input buttons
Grip mule being used to examine input face
Trigger module with haptic motor,adjustable trigger travel and linkage arm for potentiometer
Confusing myself with flippable configurations…
Trying a “Mechanical” concept with trigger, joystick and grip

Mule #1 – “Inputs”

This was built to examine the real estate available for control inputs, and the range of adjustment that could be desirable between the grip and joystick
Stripping it down to basics
Working through an idea
Exploring control inputs, this controller mule has a sliding joystick module to set ideal distance for individual hand grip
Exploring control inputs with controller mule, joystick module at minimum distance to grip
Exploring Control inputs with mule, “control module” under consideration

Tundra HDK

SteamVR™ tracking was quickly chosen because of its performance and open access at low entry cost; Tundra Labs offering a general purpose hardware development kit (HDK) ideal for building prototype equipment.
Tundra Labs schematic
Tundra Labs SteamVR HDK
Tundra Labs SteamVR HDK
Tundra Labs SteamVR HDK
Sensor flexes with numbering
Unclipping sensor flexes from backing
Sensor flexes
Battery box
Order arrived from digikey
Battery and USB connection tests

Mule #2 – “T-Bar”

This was quickly built to understand the physicality of working with the HDK specifically the sensor placement and flex management.

Locating the sensor “centroid” accurately on a stable adhesive pad was challenging; I used a number of commercial products trying to find the best solution.

Built with a single trigger to allow a simple input, I soon realized the complexity of working out my sensor locations, and moved onto a simpler idea.
T-BAR” SteamVR controller mule
Figuring out how to place sensors
Pulling gyro data from the T-Bar mule
Optical sensor data from T-Bar controller

Mule #3 – “Guncube”

After stripping down the second mule I found a suitable cardboard box to build a simple tracked object. Skarredghost suggested the name Guncube which sounded ideal.

This time I built a crude model in OpenSCAD and used valve’s SteamVR HDK tools for the first time to analyse sensor placement and understand the process in detail.
OpenSCAD training
Understanding the physicality of Sensor placement
Gungrip added to aluminium base plate
Battery retaining strap in pistol grip
Sensor flexes inside cardboard box used to build sensor box
OpenSCAD representation of “Guncube”
“Guncube” development mule with wired USB connection to PC
Pulling IMU data off “Guncube”
Lighthouse console session
SteamVR HDK design simulation tool
SteamVR HDK design simulation tool showing analysis of sensor locations
“Guncube” showing sensor locations as selected by the simulation tool, which also generates the three dimensional coordinates for building the controller JSON file

More coming soon…

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