WIP: Video: Add 4xRGSS downsampling shader.

[KrossX]

I saw the output resampling in the recent progress report, so I thought this method might be a good addition as it gives quite decent results for the number of samples.

Here's some comparison screenshots using Starfox Adventures (fur, diagonal lines) at 4x internal resolution and native window size. Album

EDIT: More screenshots. LEGO StarWars, Rythm Heaven

~~Note: Due to resampling_method numbering on the shader, I re-added the hidden methods to the enum. (Nearest, Hermite). Also, no documentation on the shader and no tooltip... therefore, WIP.~~

[Filoppi]

Nice addition. Just so you know, we already had long discussions about adding Nearest Neighbor and decided against it, it's there mostly for debugging, so just add 4GSS as index 7 and shift up nearest neighbor by 1 (to 8). Same for Hermite, i don't think it's benificial to have it exposed, it's just there to highlight it's possible.

[Filoppi]

I have no problem approving this PR now, but I'll let it sit for a while until some others had a chance of seeing it. In the meantime, could you provide some more screenshots of how this acts with downscalign and upscaling?

[KrossX]

Here's a bunch of screenshots, I think overall quality is like a cheaper Area filter, on the blurry side. LEGO StarWars, Rythm Heaven.

For upscaling, it's rather useless. Or in other words, it ain't worse than default. Default | 4xRGSS

EDIT: Xtra Zelda_WW_Screenshots.zip

For reference, here's native with 4xSSAA (looks quite nice)

[Sam-Belliveau]

Area:

RGSS:

It's close but there is noticeably more aliasing than with Area. This makes sense as its approximating Area sampling but only using a subset of the samples. I don't think it's a good idea because the limitation in speed here is not the number of samples.

[KrossX]

Roger that.