This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.
The linearVelocity
read-only property of the VRPositionState
interface returns the current linear velocity of the sensor.
This is the current velocity at which the sensor is moving, along the x
, y
, and z
axes. If the sensor is incapable of providing linear velocity, the method will return null
.
Syntax
var myLinearVelocity = VRPositionState.linearVelocity;
Value
A DOMPoint
.
Examples
The following example is taken from our velocity-acceleration demo, which uses the WebVR API to update the view of a simple 2D canvas
scene on each frame of a requestAnimationFrame
loop, while ouputting the linearVelocity
, VRPositionState.linearAcceleration
, VRPositionState.angularVelocity
, and VRPositionState.angularAcceleration
values to the UI on each frame for information purposes.
function setView() { var posState = gPositionSensor.getState(); ... linVelPara.textContent = 'Linear velocity: x' + formatNumber(posState.linearVelocity.x) + " y" + formatNumber(posState.linearVelocity.y) + " z" + formatNumber(posState.linearVelocity.z); linAccPara.textContent = 'Linear acceleration: x' + formatNumber(posState.linearAcceleration.x) + " y" + formatNumber(posState.linearAcceleration.y) + " z" + formatNumber(posState.linearAcceleration.z); angVelPara.textContent = 'Angular velocity: x' + formatNumber(posState.angularVelocity.x) + " y" + formatNumber(posState.angularVelocity.y) + " z" + formatNumber(posState.angularVelocity.z); angAccPara.textContent = 'Angular acceleration: x' + formatNumber(posState.angularVelocity.x) + " y" + formatNumber(posState.angularVelocity.y) + " z" + formatNumber(posState.angularVelocity.z); } function formatNumber(number) { number = number.toFixed(2); if(number => 0) { number = Math.abs(number); number = number.toFixed(2); number = "+" + number; } return number; }
This allows you to get an idea of how these values change as the VR headset is moved and rotated.
Specifications
Specification | Status | Comment |
---|---|---|
WebVR The definition of 'linearVelocity' in that specification. |
Editor's Draft | Initial definition |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|
Basic support | (Yes)[1] | 39 (39)[2] | No support | No support | No support |
Feature | Android | Firefox Mobile (Gecko) | Firefox OS (Gecko) | IE Phone | Opera Mobile | Safari Mobile | Chrome for Android |
---|---|---|---|---|---|---|---|
Basic support | No support | 39.0 (39)[2] 44.0 (44)[3] |
No support | No support | No support | No support | No support |
- [1] The support in Chrome is currently experimental. To find information on Chrome's WebVR implementation status including supporting builds, check out Bringing VR to Chrome by Brandon Jones.
- [2] The support for this feature is currently disabled by default in Firefox. To enable WebVR support in Firefox Nightly/Developer Edition, you can go to
about:config
and enable thedom.vr*
prefs. A better option however is to install the WebVR Enabler Add-on, which does this for you and sets up other necessary parts of the environment. - [3] The
dom.vr*
prefs are enabled by default at this point, in Nightly/Aurora editions.
See also
- WebVR API homepage.
- MozVr.com — demos, downloads, and other resources from the Mozilla VR team.