VRChat has an arbitrary limit of 2048x2048 on rendering resolution for mirrors. That works fine for something like a valve Index which has a native resolution of 1440x1600. But the 8KX has both 3840x2160 and wide FOV which far exceed this limit.
You might think this would cause the view in the mirror to be reduced to “merely” roughly the quality of the Index, but it’s actually much worse. It seems like FOV plays into it as well, so it becomes heavily pixelated and more or less unusable.
Since VRChat has already deployed EAC without fixing this, I’ve done more experimentation and figured out how to at least mitigate the problem. The more you reduce FOV and rendering resolution on the 8KX, the less pronounced the problem becomes. Paradoxically, mirrors actually become less pixelated as you lower these values.
Previously I was running large FOV with 100% resolution (5044x3160). Switching to normal FOV at 50% resolution makes mirrors merely blurry rather than pixelated all to heck.
I’m going to guess that if you weren’t noticing anything with you 8KX, you were probably already running at lower resolution and FOV. However, unless you’re running these very low, I expect that mirror quality is still being degraded for you, but perhaps not bad enough that you really noticed it. Or you just thought it was normal for mirrors to be a little fuzzy, like an intentional effect.
So what FOV and rendering resolution (in pixels) are you running at?
Foveated rendering is how I was running VRChat at 5044x3160 without the frame rate tanking.