Comment by cma
1 day ago
You still don't get the 4X increase on those pixels. You get it compressed down to a blended by coverage estimation of elements within the pixel. With a 4x higher res display instead of 4x MSAA or 4x SSAA you get more info in that area because you preserve more spatial aspects of the elements of it, instead of just coverage aspects.
Ok let's try this. In this scenario you have access to a channel with up to 4x more information than what you otherwise would have access to. Exactly how the information is sampled is application specific and will introduce variability into the final result.
If we want to get very pedantic, the information gain per pixel could actually be far more dramatic than 4x under any super sampling strategy. Assume a pathological case like a very dark room where 100% render scale doesn't have a single pixel that picks up the edge of a prop in a corner. At higher render scale maybe you start to get a handful of pixels that represent the feature. Even if you blend these poorly, you still get better than nothing. Some might argue that going from zero information to any information at all represents an infinite gain.
Depending on details of the rasterizer, at the lower resolution bits of those can still show up at the same rate, just with more frames not catching any of them.
If it's just one pixel of it showing up, when it is picked up it is likely overrepresented, so may represent a loss rather than a gain relative to the baseline where it perfectly supersampled it would say show up with 0.1% intensity.
The all black frames may be more accurate relative to baseline than the ones that pick it up with much stronger intensity.
If the feature perfectly supersampled would show up with 50.1% intensity the frames with it may be more accurate than the frames without it, but now it will be more common.