Custom Resolution Question

[Highstriker]

Okay, so I'm refining my settings and a friend's question made me take a closer look, some clarification would be great.

Okay I'm using the old Rift CV1, and each eye renders at 1080x1200
I use Custom Resolution in SteamVR. When it's set at 100% (Which I assumed was like zero. 1:1 with the Rift) it says "each eye will be rendered at: 1644x1960"
So if I bring it down to 42%, that's the closest I can get to 1:1 with my rift, at 1024x1268.

What exactly is going on here?
For testing purposes, if I want -no- multiplier, should I lower this as close to my real resolution as I can? Or is 100% actually the same as zero; or: "this is the same as no multiplier"
and anything under 100% is actually negative resolution?

[Bob Loblaw]

For comparison, a vive also has 1080 x 1200 screens in the headset. 100% steamvr resolution has the GPU render (for the vive) at 1512x1680 pixels, not far from your numbers. This image then undergoes a major barrel distortion transform onto the smaller HMD screen, to cancel out the lens distortion. There is not a uniform pixel-to-pixel relationship at this point, with the center and edges having very different pixel densities remaining from the original image. The higher render resolution makes sure there's real pixels being rendered for the portions of the image that would otherwise get starved for pixels by the distortion transform.

So: There is no 1:1 possible over the whole image. There is not a uniform ratio over the whole image, the edges actually get most of the rendered pixels. If you keep the render at 100% or above, your HMD screen is getting the pixels it was designed for. If you go below 100%, you are poorly utilizing your HMD screen's pixels, starting with the center getting fuzzy first. If your GPU can handle more than 100, it'll look better.

Here's an explanation on youtube:
https://www.youtube.com/watch?v=B7qrgrrHry0

[Highstriker]

Very informative! But one more question or clarification, what setting would be similar to not using custom resolution? 100, 42, or 0 (custom resolution not used)? I'm trying to find a zero point, and see how far I can go from zero.

From what I'm reading above, 100% is perfectly ideal. Is that the same as if custom resolution is not being used?

edit: I mean, with 100%, is that the same as using a non steamvr game at default optimal settings where custom res isn't offered?

Thank you very much Bob Loblaw.

[Bob Loblaw]

42 is going to look low res. 100% the best place to start. If you aren't bothered by aliasing in the game, leave it. But if straight lines are too jaggy, you can turn supersampling (steamvr resolution) up to fight that, until you turn it up too much and reprojection starts to happen because your GPU can no longer keep up with the frame rate.

If it's blurry, turn it up. If it's jerky, turn it down. If you can't find a sweet spot, you might want to consider a faster GPU (or CPU, depending on the game, :cough: Fallout :cough:).

SteamVR settings>Video>Advanced Frame Timings will open a fancy graph on your desktop, with a checkbox to Show in Headset. Check it and the back of your right wrist will show frame timings in game, and rendering times on both CPU and GPU. Reprojection will kick in over 11 ms, so if a game is making frames in 5ms, I crank up the supersampling.

FWIW I have to run fallout at 86%, everything else I run at 100 or more. I was in Viveport Video (which has jaggy straight white lines around menu boxes, also changes supersampling on the fly), which was rendering frames in 3 ms at 100%, I bumped it to 140%, and again to 240%, and the jaggy reduction between those last two settings amazed me.

[Benn]

my vive cosmos elite has a 100% resolutiton of 3460 x 4084 Pixels per godam eye wich make my games very hard to run even with my rtx 4080 :(