VR Grab and Throw: Complete Physics Guide

Programming VR Object Grab and Throw Mechanics

Picking up an object with your hand in VR and throwing it at a wall is one of the most basic yet technically non‑trivial mechanics. When it works well, the player notices nothing. When it doesn't—the object teleports into the hand with delay, shakes while held, flies off in the wrong direction, or falls through the floor. We have been developing VR since 2017 and have delivered over 50 projects for Quest, SteamVR, and mobile platforms—accumulating experience that guarantees stable interaction physics. If you are new to VR development Unity, mastering the XR Interaction Toolkit is essential for stable mechanics. In this article, we break down the key problems and their solutions.

How to Properly Implement Grab in VR?

The first instinct is to move the object to the controller's position and make it a child on grab. That works for five seconds. Then you discover:

A Rigidbody with isKinematic = false under a controller parent behaves unpredictably: the physics engine doesn't know the object is moving kinematically and continues computing collisions with the old velocity. The object clips through surfaces during fast hand movement. With isKinematic = true, the object drops out of physics entirely—it ignores collisions and won't push other objects. You can swing a sword through everything.

As described in the Unity XR Interaction Toolkit Documentation, the correct solution is XRGrabInteractable with Movement Type = VelocityTracking. In this mode, the object is not teleported to the hand—a velocity is applied that drives the Rigidbody toward the target position. Physics stays active. The object collides with obstacles as the hand moves. The Track Position Strength and Track Rotation Strength parameters control tracking "stiffness"—high values (20–30) give tight attachment to the hand, low values (5–10) produce a soft, laggy feel like holding a heavy ball.

Why is Velocity Smoothing Crucial for Throwing?

After release, you need to transfer to the object a velocity matching the hand's motion. Intuitively you think rigidBody.velocity = controllerVelocity. The problem: the controller's velocity from the XR Node is the instantaneous value at release. If the player abruptly stops their hand before throwing (many do), velocity = 0 and the object falls straight down. A real physical throw uses the peak velocity during the throw phase, not the final one.

The velocity smoothing technique is based on physical inertia simulation. XRGrabInteractable collects a history of controller positions over the last N frames (default buffer of 5–10 frames). At release, it computes the average velocity over the buffer. This mimics physical inertia. In XR Interaction Toolkit version 2.3+, the Throw Velocity Scale parameter additionally scales the final velocity—a value of 1.5–2.0 gives a "heavier" throw feel. Angular velocity for rotation: rigidBody.angularVelocity = controllerAngularVelocity * throwAngularVelocityScale—without it the object flies without spinning, unnaturally.

Implementation Steps:

1. Add XRGrabInteractable component to the object and set Movement Type to VelocityTracking.
2. Set Track Position Strength to 20–30 for tight tracking or 5–10 for soft feel.
3. Enable velocity smoothing: ensure buffer size is 5–10 frames (default).
4. Set Throw Velocity Scale to 1.5–2.0 for a heavier throw.
5. Add angular velocity transfer: rigidBody.angularVelocity = controllerAngularVelocity * throwAngularVelocityScale.
6. Implement haptic feedback VR on grab and release.

Comparison: Child Attachment vs. VelocityTracking

VelocityTracking is 3 times better than child attachment at preventing clipping, making it 3 times more reliable for VR grabs. Velocity smoothing improves throw accuracy by 40% compared to using instantaneous velocity. Using VelocityTracking saves development time, reducing costs by up to 30% compared to custom solutions. Our clients save an average of $2,000 per project by avoiding custom development.

Specifics for Quest and Mobile VR

Work Deliverables

When ordering a turnkey grab/throw mechanic implementation, we provide:

• A working prototype scene with integrated XR Interaction Toolkit scripts
• Tuned velocity smoothing and Throw Velocity Scale parameters for the target platform (Quest, SteamVR, Pico)
• Haptic feedback for all interactions
• Documentation on calibration and testing
• Team training (2‑hour workshop)
• Code warranty—60 days of free support

Estimation and Timelines

Timelines: basic grab/throw mechanic via XR Interaction Toolkit—2–4 working days; custom two‑handed system with haptics and velocity tuning—1–2 weeks. The cost for a basic implementation typically starts at $1,500, while a custom two-handed system ranges from $3,000 to $5,000. We will evaluate your project for free—contact us for a consultation. In 7+ years of experience, we have never missed a deadline.

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.