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.
let framebuffer = xrWebGLLayer.framebuffer;
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
getFramebufferAttachmentParameter()on an opaque framebuffer results in the WebGL error
- 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_OPERATIONerror (0x0506). Calling
checkFramebufferStatus()on the WebGL context from outside the animation frame callback causes the WebGL
FRAMEBUFFER_UNSUPPORTEDerror (0x8CDD) to be reported.
- Opaque framebuffers initialized with the
depthproperty set to
falsewill not have a depth buffer and will rely on the coordinates alone to determine distance.
- Opaque framebuffers initialized without specifying a
stencilwill not have a stencil buffer.
- Opaque framebuffers will not have an alpha channel available unless the
truewhen creating the layer.
- The XR compositor assumes that opaque framebuffers use colors with premultiplied allpha, regardless of whether or not the WebGL context's
premultipliedAlphacontext attribute is set.
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.
This example gets the
XRWebGLLayer for a session and then passes its framebuffer into the WebGL context's
let glLayer = xrSession.renderState.baselayer; gl.bindFramebuffer(gl.FRAMEBUFFER, glLayer.framebuffer);
|WebXR Device API
The definition of 'XRWebGLLayer.framebuffer' in that specification.
|Working Draft||Initial definition.|
|Chrome Full support 79||Edge Full support 79||Firefox No support No||IE No support No||Opera No support No||Safari No support No||WebView Android No support No||Chrome Android Full support 79||Firefox Android No support No||Opera Android No support No||Safari iOS No support No||Samsung Internet Android Full support 11.2|
- Full support
- Full support
- No support
- No support