The fixedFoveation property of the XRWebGLLayer interface is a number indicating the amount of foveation used by the XR compositor. Fixed Foveated Rendering (FFR) renders the edges of the eye textures at a lower resolution than the center and reduces the GPU load.
It is most useful for low contrast textures, such as background images but less for high contrast ones such as text or detailed images. Authors can adjust the level on a per frame basis to achieve the best tradeoff between performance and visual quality.
A number between 0 and 1.
- The minium amount of foveation is indicated by 0 (full resolution).
- The maximum amount of foveation is indicated by 1 (the edges render at lower resolution).
It's up to the user agent how to interpret the numbers in this range. When changing the foveation level, the effect will visible in the next XRFrame.
Note that some user agents might implement certain levels of foveation, so you might need to adjust the foveation level in large increments to see an effect. Example levels:
-
0: no foveation -
1/3: low foveation -
2/3: medium foveation -
1.0: maximum foveation
Some devices don't support foveated rendering. In that case fixedFoveation is null and setting it will not do anything.
The fixedFoveation property allows you to set the level of foveation at runtime and for each frame. To set the maximum foveation for a given XRWebGLLayer, use a value of 1.
let glLayer = xrSession.renderState.baseLayer;
glLayer.fixedFoveation = 1;