XRWebGLLayer: framebuffer property
The read-only XRWebGLLayer
property framebuffer
is an opaque WebGLFramebuffer
which is used to buffer the rendered image if the XR compositor is being used. Otherwise, this property's value is null
. The opaque framebuffer is functionally nearly the same as a standard WebGL framebuffer, except for the differences covered in the section How opaque framebuffers are special below.
Value
A WebGLFramebuffer
object representing the framebuffer into which the 3D scene is being rendered, or null
if the XR compositor is disabled for the session.
Usage notes
How opaque framebuffers are special
The framebuffer represented by the framebuffer
property is opaque. As such, its behavior is different in several ways from a standard WebGL context. These differences cause the opaque framebuffer to behave more like the default WebGL framebuffer:
- Opaque framebuffers may support anti-aliasing, even under WebGL 1.0, which don't normally do so.
- Opaque framebuffers' attachments (buffers and the like) can't be inspected or changed. Calling functions such as
framebufferTexture2D()
, framebufferRenderbuffer()
, deleteFramebuffer()
, or getFramebufferAttachmentParameter()
on an opaque framebuffer results in the WebGL error INVALID_OPERATION
(0x0502). - Opaque framebuffers are considered incomplete and are not available for rendering other than while executing the
requestAnimationFrame()
callback. Attempting to clear, draw to, or read from the framebuffer results in a WebGL INVALID_FRAMEBUFFER_OPERATION
error (0x0506). Calling checkFramebufferStatus()
on the WebGL context from outside the animation frame callback causes the WebGL FRAMEBUFFER_UNSUPPORTED
error (0x8CDD) to be reported. - Opaque framebuffers initialized with the
depth
property set to false
will not have a depth buffer and will rely on the coordinates alone to determine distance. - Opaque framebuffers initialized without specifying a
stencil
")}}` will not have a stencil buffer. - Opaque framebuffers will not have an alpha channel available unless the
alpha
property is true
when creating the layer. - The XR compositor assumes that opaque framebuffers use colors with premultiplied alpha, regardless of whether or not the WebGL context's
premultipliedAlpha
")}}` context attribute is set.
Note: The depth
and stencil
properties are not required to be supported in order for a browser to be construed as having full WebGL support.
The default configuration of a new framebuffer
Upon creating a new XRWebGLLayer
, its new framebuffer is initialized just like the default framebuffer for any WebGL interface:
- The color buffer is configured with its clear value set to the color (0, 0, 0, 0) (meaning transparent black).
- The depth buffer's clear value is the number 1.0.
- The stencil buffer is filled with 0.
Examples
This example gets the XRWebGLLayer
for a session and then passes its framebuffer into the WebGL context's bindFramebuffer()
function.
let glLayer = xrSession.renderState.baselayer;
gl.bindFramebuffer(gl.FRAMEBUFFER, glLayer.framebuffer);
Specifications
Browser compatibility
|
Desktop |
Mobile |
|
Chrome |
Edge |
Firefox |
Internet Explorer |
Opera |
Safari |
WebView Android |
Chrome Android |
Firefox for Android |
Opera Android |
Safari on IOS |
Samsung Internet |
framebuffer |
79 |
79 |
No |
No |
66 |
No |
No |
79 |
No |
57 |
No |
11.2 |
See also