Integrating Eye Tracking into VR: FFR, Gaze, Calibration

Over five years, we have completed more than 20 Eye Tracking integrations in VR projects — from prototypes on Quest 3 to enterprise solutions on Varjo XR-3. The main pain point for clients is a tight GPU budget, with Fixed Foveated Rendering saving only 10–15%. Dynamic FFR with Eye Tracking squeezes out up to 25% performance. However, simply connecting the SDK and reading gaze direction is not enough: raw data is noisy, requires filtering, and each interaction type needs its own logic. Our engineers are Meta XR and OpenXR certified, ensuring stable operation across all supported headsets.

Platforms and SDKs

Meta Quest Pro / Quest 3

Meta provides Meta Movement SDK (formerly OVRPlugin). The OVREyeGaze component and low-level OVRPlugin.GetEyeGazesState() allow you to obtain gaze direction, eye openness, and pupil dilation. Accuracy after calibration is ±1.5–3°. Permission must be requested via OVRPermissionsRequester before use.

OpenXR

The cross-platform pathway uses the XR_EXT_eye_gaze_interaction extension. In Unity, connect via XR Interaction Toolkit 2.3+ — GazeInteractor and GazeInteractable. One codebase for all OpenXR-supported headsets: from Quest Pro to Varjo. This reduces maintenance costs and pays off on multi-platform projects.

Tobii XR SDK

For older PC headsets (HTC Vive Pro Eye), the Tobii XR SDK is used. It is an official Unity package but integrates via Windows Mixed Reality. Separate calibration setup is required.

Platform Comparison

Comparison of Gaze Data Filtering Methods

How EyeTracked FFR Works

Fixed Foveated Rendering (FFR) renders the periphery at lower resolution, but the center is fixed. Dynamic FFR shifts the high-quality zone with the gaze. On Quest 3, this yields a 15–25% GPU boost — the difference between 72 and 90 FPS in heavy scenes.

Connecting in Unity via OpenXR: enable XR_FB_foveation and XR_FB_foveation_vulkan. For Meta SDK — set OVRManager.eyeTrackingEnabled = true and combine OVRManager.fixedFoveatedRenderingLevel with OVRPlugin.useDynamicFixedFoveatedRendering. Dynamic FFR outperforms Fixed FFR by 20–30% in GPU savings while maintaining quality at the point of gaze.

Why Gaze Cursor Needs Filtering

Raw gaze data contains high-frequency noise of ±0.5–1°. Without filtering, the object under the gaze flickers between selected/unselected. Solution: exponential filter.

// Exponential filter for gaze cursor
smoothedGaze = Vector3.Slerp(smoothedGaze, rawGaze, smoothFactor * Time.deltaTime);
// smoothFactor ≈ 10–15

Additionally, dwell time activation: an object activates if the gaze is held longer than 0.5–1.5 seconds. A visual indicator — arc/ring around the object.

Permissions and Privacy

Eye Tracking requires special permissions in Meta Developer Hub. For publication in Meta Store, a separate policy review is needed: the app must not transmit raw eye data to a server without explicit user consent. In Unity, handle OVRPermissionsRequester and check OVRPlugin.eyeTrackingEnabled. For enterprise solutions, separate legal documentation is required.

What's Included in the Work

• Requirement analysis and optimal SDK selection
• Eye Tracking setup on the target headset
• Gaze cursor implementation with filtering and dwell time
• Dynamic Foveated Rendering integration (if supported)
• Attention analytics collection (heatmaps, gaze duration)
• API documentation and team training
• Post-release support (1 month)

Process and Timeline

1. Analysis: determine the platform, SDK, and required permissions (1–2 days).
2. Design: choose filtering and interaction approach, prototype (2–3 days).
3. Implementation: integrate SDK, set up FFR, gaze logic (4–8 days).
4. Testing: verify accuracy, FPS measurements, usability (2–3 days).
5. Deployment: build for the target platform, deliver sources and documentation.

Estimated timelines: basic integration (gaze cursor + selection) — 2–4 working days; full (Dynamic FFR + analytics) — 1–2 weeks. The cost depends on complexity and required functionality — contact us for a project assessment. The investment pays off through increased performance and reduced costs for adapting the application to different headsets.

Get a consultation for your VR project: we will analyze the requirements and propose the optimal solution considering your stack and budget. Our engineers have 5+ years of experience and Meta XR certification.

VR and AR Development

When we first launch a project in a VR headset, most teams face the same thing: technically everything works, but in the headset either motion sickness occurs, or hands 'float' with a delay, or the scene looks jerky at the periphery. These are not bugs in the usual sense — they are a consequence of the fact that VR/AR development requires a different approach to render architecture, interaction, and UX from the very beginning of the project. Our experience: over 7 years in game dev, 15+ completed VR/AR projects for Meta Quest, SteamVR, PSVR2, HoloLens. We work with teams that need not just a prototype but a production‑ready application with a stable frame rate.

Platforms and SDKs

We work with all relevant stacks. We use OpenXR as the base layer wherever possible — it provides cross‑platform compatibility between Meta, Valve Index, HP Reverb and other PC VR devices. On top of OpenXR, we build on the XR Interaction Toolkit (Unity) or VR Expansion Plugin (Unreal). Contact us for a stack assessment tailored to your project.

How to minimize motion sickness in VR locomotion?

Locomotion — the main source of motion sickness for inexperienced VR users. According to research, about 70% of users experience discomfort with improper movement settings Oculus Developer Guidelines. Teleportation — standard navigation method when smooth movement is undesirable.

Components from XR Interaction Toolkit: TeleportationArea, TeleportationAnchor, TeleportationProvider. Basic implementation works out of the box, but for production we refine it in four steps:

1. Setting up XRRayInteractor with a curved ray (Bend Ray) — the teleportation arc looks more natural than a straight ray and is perceived better by users.
2. Adding a valid landing zone — a visual indicator changes color when hovering over an obstacle (red/green).
3. Implementing fade transition — smooth screen fade (black fade) before teleportation reduces disorientation.
4. Rotation snapping — after teleportation we offer snap rotation by 45° or 90° instead of smooth, reducing motion sickness risk.

For projects requiring smooth locomotion (action games, simulators), we use comfort settings: vignetting during movement, reducing FOV during acceleration. Settings are available to the user in the menu — different people have different sensitivity thresholds. The difference between kinematic and physics‑based movement: kinematic gives instant hand following but lets objects pass through walls; physics‑based via Joint provides realistic collisions but requires velocity damping and max joint force tuning. We choose based on the type of interaction.

How to make object grabbing in VR physically realistic?

This is the most underestimated part of VR development. Clients often perceive it as 'just hand animation', but in practice it is a complex system where physical correctness, responsiveness, and comfort conflict.

Grab (grabbing)

XR Interaction Toolkit provides three types of Interactable for grabbing:

• XRGrabInteractable — standard grab, object follows controller via physics joint or direct position/rotation
• XRSimpleInteractable — for objects without physical movement (buttons, levers)
• Custom Interactable by inheriting from XRBaseInteractable

Attach Transform — a frequently ignored detail. Each Interactable must have a properly configured Attach Transform (the point where the hand 'attaches'). Without it, the pistol grip will be at the center of the mesh, not where it is held.

For weapons and tools with two‑handed grab — a separate TwoHandGrab system: leading hand determines position, the second — orientation. XR Interaction Toolkit supports this via XRTwoHandGrabInteractable or custom logic with two Attach Points.

Throw (throwing)

Velocity smoothing is critical for realistic throwing because the Rigidbody.velocity at the moment of controller release reflects instantaneous speed, often incorrect due to tracking discretization. The user makes a quick wrist movement — but the object flies half as fast.

Solution: velocity smoothing over the last N frames (typically 5–10 frames, ~80–160 ms at 60 Hz) before release. XR Interaction Toolkit does this via VelocityEstimator. Additionally, we apply a velocity scaling multiplier — a small speed increase (1.2–1.5×) makes throws subjectively more satisfying. Angular velocity (for objects that should spin in flight) is also averaged similarly.

AR: Plane Tracking and Environment Interaction

AR adds a different class of problems — working with real, unpredictable environment. AR Foundation — a cross‑platform layer on top of ARKit and ARCore. Most basic features (plane detection, raycasting, image tracking, face tracking) are available through a unified API.

Plane Detection

ARPlaneManager detects horizontal and vertical planes. Practical nuances:

• Initialization takes time — the user must look around the room while the system builds a map. An explicit onboarding with instruction 'slowly move the camera across surfaces' is needed.
• Planes are unstable — their boundaries and position are updated as data accumulates. Objects placed on a plane need to be attached via parent to ARPlane, not to world coordinates.
• Plane merging — two detected floor segments may merge into one, moving the anchor. For critical anchors, use ARAnchor instead of direct attachment to the plane.

Image tracking (via ARTrackedImageManager) quality directly depends on the quality of reference images. Images with high detail frequency and contrasting edges (like a QR code but stylish) track more reliably than smooth logos. ARCore Geospatial API — for outdoor AR with real‑world coordinate binding (accuracy up to 10 cm in well‑mapped areas).

Optimization for VR: Frame Rate and Comfort

VR requires stable high frame rate. About 60% of development time in mobile VR goes to optimization, not functionality — retrofit costs twice as much as proper architecture from the first sprint.

Single Pass Instanced Rendering

The main render optimization in VR. Without it, the scene is rendered twice (once per eye), doubling draw calls. Single Pass Instanced renders both eyes in one pass via instancing: geometry is processed once, the shader gets two view/projection matrices through GPU instancing. Enabled in Unity via XR Plug-in Management > Rendering Mode: Single Pass Instanced. Important: custom shaders must support SPI — standard URP/HDRP shaders support it, custom HLSL requires modifications (UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX and related macros). Applying this technique reduces draw calls by 40–50%, making it twice as efficient as naive double rendering.

Foveated Rendering

On Meta Quest, Fixed Foveated Rendering (FFR) is available — reducing resolution at the periphery where visual acuity is lower. Configured via OVRManager or Meta XR SDK:

OVRManager.fixedFoveatedRenderingLevel = OVRManager.FixedFoveatedRenderingLevel.High;
OVRManager.useDynamicFixedFoveatedRendering = true;

Dynamic FFR automatically increases the level when frame rate drops — more convenient than fixed in scenes with variable load.

IPD and Comfort Settings

IPD (Inter‑Pupillary Distance) — affects depth perception. At the programmable level on most devices, only reading IPD is available (OVRPlugin.GetSystemDisplayFrequency), physical adjustment is on the headset. For applications requiring precise positioning (medical simulators, training), we account for IPD in scene scale calculations.

Haptics

Haptic feedback — an underestimated tool. Even a simple vibration response when grabbing an object or hitting significantly increases the sense of presence. On average, integrating haptic patterns takes 30–80 hours per project.

XR Haptics via OpenXR:

var hapticImpulse = new UnityEngine.XR.HapticCapabilities();
InputDevice device = InputDevices.GetDeviceAtXRNode(XRNode.RightHand);
device.SendHapticImpulse(0, amplitude: 0.5f, duration: 0.1f);

For complex patterns (tactile 'texture' of a surface when touched, increasing vibration when drawing a bowstring) we use Meta Haptics Studio — allows designing haptic clips visually. This can reduce time spent on manual haptic tuning by about 30%.

What does VR/AR application development include?

When ordering a turnkey project, we provide the following deliverables:

• Architectural document with stack description, render logic, and interaction system
• Working prototype (MVP) for testing on target device
• Integration of necessary SDKs (Meta XR, OpenXR, AR Foundation, etc.)
• Optimization for target frequencies 72/90/120 Hz with draw call and FPS profiling
• Testing on physical hardware (Quest, SteamVR, HoloLens) with user involvement
• Full documentation for build, deployment, and support
• Training for the client's team (workshop on XR Toolkit)
• Warranty support for 1 month after delivery

What affects cost and timeline?

VR/AR projects are more expensive than regular games of similar scope. Iterations are slower — each fix must be tested in the headset, an emulator does not convey the real experience. Motion sickness forces reworking some conceptual decisions after the first playtest. Optimization takes a significant portion of time — for mobile VR (Quest) up to 60–70% of the cycle. For Quest projects, we start optimization from the first sprint. The cost of basic SDK integration (XR Interaction Toolkit) varies depending on the scope of custom Interactable. Typical budgets for a full Quest project range from $25,000 to $80,000 depending on complexity, number of custom interactions, and depth of optimization. Proper architectural planning from sprint one typically saves 40% on later rework compared to fixing performance bottlenecks retroactively.

Get a consultation on your project — we will assess the task, stack, and timelines. Order turnkey VR/AR application development with a guaranteed stable frame rate.