VR Dasher — Eye Tracking Text Input for Meta Quest

An eye-tracking text input system based on the Dasher algorithm, built in Unity for Meta Quest VR headsets.

Requirements

• Unity Editor: 2022.3.62f3
• Git (for cloning and version control)
• Internet connection on first open so Unity can restore packages from Packages/manifest.json

The exact Unity version is recorded in ProjectSettings/ProjectVersion.txt. Using the same 2022.3 LTS line is usually fine, but the safest option is the exact editor version above.

What is Dasher?

Dasher is a text input method where you don't type — you steer through characters using your gaze (or mouse). Characters are arranged vertically, sized by their probability of being next. You "zoom" right to select, left to undo. A language model predicts likely next characters and makes them bigger = easier to select.

Quick Start (Unity Editor — No VR Needed)

1. Open Unity Hub → Add project from disk → select this VrDasher2/ folder
2. Use Unity 2022.3.62f3 if possible
3. Let Unity restore packages and import the project fully on first open
4. Create a new Scene (File → New Scene)
5. Create an empty GameObject → Name it DasherSystem
6. Add Component → search for DasherSceneSetup → attach it
7. Press Play
8. Move your mouse:
   • Right → zoom into characters (select)
   • Left → zoom out (undo)
   • Up/Down → choose which character
   • Backspace → clear all text
   • Space → pause/resume

Project Structure

Assets/Scripts/
├── Core/
│   ├── DasherEngine.cs        # Core zooming algorithm (OneStepTowards)
│   ├── DasherNode.cs          # Tree node with bounds & colors
│   ├── DasherRenderer.cs      # UI rendering with object pooling
│   └── LanguageModel.cs       # PPM order-5 prediction model
├── Input/
│   ├── IDasherInput.cs        # Input interface
│   ├── MouseInput.cs          # Mouse (Editor testing)
│   ├── HeadGazeInput.cs       # Head gaze (Quest 2/3)
│   ├── EyeTrackingInput.cs    # Eye tracking (Quest Pro)
│   └── GazeCursor.cs          # Visual gaze cursor
├── DasherController.cs        # Main controller (auto-detects input)
└── DasherSceneSetup.cs        # One-click scene builder

How the Algorithm Works

1. Language Model (PPM order-5) predicts next character probabilities from training text
2. Character boxes are sized proportionally to their probability
3. Pointer position controls zoom: right = forward (write), left = reverse (undo)
4. The zoom algorithm (OneStepTowards) maps target range [Y-X, Y+X] to fill [0, MAX_Y=4096]
5. After a character is selected (node covers crosshair), predictions update based on new context
6. Common words like "the" require minimal effort — 'e' after "th" takes ~48% of the screen

Input Modes

Mode	Device	How It Works
Mouse	Unity Editor	Mouse position on screen → canvas position
Head Gaze	Quest 2/3	Camera forward direction → raycast onto canvas
Eye Tracking	Quest Pro	OVREyeGaze transform → raycast onto canvas

The system auto-detects the best available input — no configuration needed.

Dependency Notes

This repository should include:

• Assets/
• Packages/manifest.json
• Packages/packages-lock.json
• ProjectSettings/

This repository should not include:

• Library/
• Temp/
• Obj/
• Logs/
• UserSettings/
• local IDE files

Unity will automatically restore package dependencies from Packages/manifest.json and Packages/packages-lock.json when someone opens the project. That means people usually do not manually download normal Unity packages before opening.

One exception here is Meta XR Core SDK:

• It is optional for basic editor testing and head-gaze fallback
• It is needed if someone wants full Meta-specific VR or Quest Pro eye-tracking setup in the headset
• The current code compiles without it because the eye-tracking path uses reflection and fallback behavior

Unity Version Compatibility

• Best option: open with 2022.3.62f3
• Usually okay: another 2022.3.x LTS version
• Riskier: 2021, 2023, or 6000.x because Unity may upgrade project files or package behavior

If someone opens the project in a different major or minor Unity version, Unity may:

• reserialize project settings
• upgrade package versions
• change generated files
• make the project harder to reopen in the old version

For that reason, it is a good idea to mention the required Unity version clearly in the GitHub repo.

VR Setup (When Meta Quest Headset Available)

For Head Gaze (Quest 2/3)

1. Install Meta XR Core SDK from Unity Asset Store
2. Add OVRCameraRig prefab to the scene
3. The HeadGazeInput auto-detects VR mode — works out of the box

For Eye Tracking (Quest Pro)

1. Install Meta XR Core SDK via Package Manager
2. Add OVRCameraRig prefab to scene
3. On OVRManager, enable Eye Tracking under Quest Features → General
4. Create two empty GameObjects → Add OVREyeGaze component to each
   • Set one to Eye.Left, the other to Eye.Right
5. In DasherSceneSetup or manually: assign the eye gaze objects to EyeTrackingInput
6. On the headset: Settings → Movement Settings → Eye Tracking → Enable + Calibrate

Building for Quest

1. File → Build Settings → Android → Switch Platform
2. Ensure XR Plug-in Management → Oculus is checked
3. Player Settings → Min API Level = 29, Target = 32
4. Build and Run (connect Quest via USB or Oculus Link)