Google gives me this:
For those that don't understand, a simple way to look at Resolution Scaling is that you set the game into a windowed mode then full-screen that. Let's say your screen is 1280x720 pixels, you set the "windowed mode" resolution to 640x480, then full-screen the 640x480 rendering
Source
Implementation-wise, you simply render to a texture at lower resolution than the screen, then render that texture to the screen.
Many render techniques nowadays involve post processing, so by default you render to a texture with the same resolution as the screen, apply some changes (blur, bloom, flares, etc), then send the whole thing to the screen.
To speed up performance you can make that intermediate texture a lower resolution than the screen. You can then decide to apply the post processing to the same low resolution, or if you want to apply post processing to a high resolution image.
If there is a "Resolution Scaling" setting that allows higher resolution (200%) and doesn't remove anti aliasing, that can have 2 possible causes:
- Some sources of aliasing don't simply disappear by using twice the resolution. (that's why some anti aliasing settings allow you to specify 2x,4x,8x,16x)
- Some aliasing may be part of the post processing effects which may run at the target resolution.
I'd really need to see a screenshot to make an educated guess at what's going on.