Submerged Upscaled Viewport Plans (Patreon)

While upscaling the foggy viewport was easy, the current screen warping that's used for the submerged (underwater) effect is not directly compatible with my viewport upscaling algorithm.

Also, it works backwards: first the viewport is warped in its unscaled (lower) resolution, and then a slight upscaling is applied to eliminate wraparound.

I'm going to change the entire thing to work the other way around, warping the full video resolution coordinates and then downscaling them to the reduced viewport resolution coordinates per pixel. This way, when the viewport resolution is reduced, the screen warping will always be at full resolution, just like the fog. And this should have zero impact on performance, since the viewport upscaling will be precomputed together with the upscaling that's used to eliminate wraparound.

If that sounds a little confusing, that's because scaling "up" and "down" is relative: When you downscale the input coordinates, the image output is being upscaled (because when you walk in smaller steps, the amount of steps to cover the same area will be bigger). Similarly, upscaled coordinates downscales the image.