framebuffer is an opaque
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.
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
- 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
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 |
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