this would be a nice feature: run game at a huge res, let gpu scale down

[Ben90]

I haven't used a Nvidia card thoroughly since my 7800GTX. Wouldn't forcing super sampling from something like nHancer be easier and more reliable than letting the monitors scaler do its thing? A few games won't even let you select 2560x1600, much less 3840x2160.

 

[boxleitnerb]

Well, there are two SSAA types.

1. OGSSAA (ordered grid SSAA). It's simply using a higher resolution and scaling it down. No fancy sampling grids, therefore the smoothing effect on textures and polygon edges is not very good compared to MSAA and SGSSAA, but at least it applies to everything. The old hybrid modes (16xS, 32xS) and the pure SSAA modes (3x3, 4x4, 2x1...) did exactly that. In principle these modes are still usable, but in my experience they don't always work with modern games.
   
   Downscaling is exactly the same, the only difference being that it doesn't require ANY support from the game. For example it works great in GTA4. Besides some older games, every single game I play let me select 3840x2160 without problems.
2. SGSSAA (sparse grid SSAA). It is built upon MSAA, using its sampling pattern. Thus, working MSAA is a prerequisite for SGSSAA. It has a much better image quality/performance ration than OGSSAA, but there are two drawbacks:
   
   
   

   • It doesn't work in every game as MSAA doesn't work in every game
   • It may be a bit blurry (differs from case to case)

To sum up:


Use SGSSAA whenever possible. Use downscaling when no MSAA is possible. You can add SMAA/FXAA/MLAA and get a very decent image quality.

 

[plonk420]

What card, what display?
With a 580 I can do this:

[snip]

With a 120Hz display and/or Kepler (GTX600) you can reach 3840x2160@60Hz.
2880x1800@1440x900 should be perfectly doable with any card. Question is if the monitor will play along.

ah, it's just a crap 60hz Asus (VH198T), on a GTX560. i thought the scaling was done card-side...

edit: also, is there a guide as to how to do SGSSAA or OGSSAA? i'm also a bit fuzzy as to whether a program like FRAPS would see the pre-downscaling image (for screenshotting purposes) and if the Nvidia tool will offer either option.

edit2: also, how front porch and sync width is calculated (or if the gpu control panel automatically calculates it and/or fills it in...

 

[boxleitnerb]

The scaling usually is done through the card, but as far as I know, the driver is limiting that somehow. For example with the same monitor, with a GT520 (!) (which has a VP5, maybe that is important) 3840x2160@60 Hz is perfectly possible. Put in a GTX580 and it suddenly is not. It's still some mystery I have to admit.

What happens when you select 2880x1800@60 Hz? You have to increase the total pixels (vertical) for higher resolutions to work. Standard on my screen is 2200 but as you see I'm using 2800 for 4K. Also you can lower total pixels (horizontal) to the bare minimum (in my case from 1125 to 1090) to get more headroom. Under no circumstances can you go past the 165 MHz DVI limit. If I reach any value above 165 MHz, I get a black screen or the test fails.

FRAPS sees the pre-downscaling image, yes. If you want to make screenshots that show what you're actually seeing on screen you have to downscale the screenshot manually, for example with FastStone Photo Resizer and a Lanczos filter.

SGSSAA is pretty straight forward. Basically there are two cases:

a) Game supports MSAA. You select SGSSAA via NV Inspector and adjust the LOD accordingly (-0.5 for 2xSGSSAA, -1.0 for 4xSGSSAA and -1.5 for 8xSGSSAA). LOD adjustment currently only works in DX9. DX10/11 support is coming with R310 drivers afaik.

Example (8xMSAA ingame selected):

b) Game doesn't support MSAA or you want to reduce blur (which can happen with SGSSAA when it collides with post processing effects). Then you would have to use AA compatibility bits.

Example 1 (forced 4xSGSSAA):


Note that I have forced MSAA which is required for SGSSAA to work. Forcing MSAA only vs. SGSSAA can require different compatibility bits.

Example 2:
Just selecting SGSSAA works, but it's blurry. Custom compatibility bits reduce/disable the blur. Sometimes this also can result in better smoothing of certain edges but with increased cost in VRAM and performance.



OGSSAA as a traditional AA method via the driver is basically dead nowadays. I would always use SGSSAA when possible, even with older games. If you want to give it a try anyway (only DX9 and older obviously as since DX10 it is not possible to force AA modes anymore) select one of these modes:

Comprehensive list of AA compatibility bits for MSAA and SGSSAA:
http://www.forum-3dcenter.org/vbulletin/showthread.php?t=490867

As for the front porch, sync and other values, I have no idea. The only thing I change is the target resolution at the top, the refresh rate and the total pixels (horizontal and vertical).

A note on the refresh frequency:
Some monitors (for example my LG IPS235) usually don't support much lower frequencies than 60 Hz. In my case, 56 Hz was the default limit and I could not use 3840x2160@54 Hz. I had to make a modified monitor driver that exposes lower frequencies. A video tutorial can be found here:

http://www.oc-burner.de/ftp/Videos/Downsampling/EDID/EDID.html

You will need three tools for that:

1. SoftMCCS
2. Phoenix EDID Designer
3. Monitor Asset Manager

All three are freeware and can be easily found on the web. Just follow the tutorial and you'll be fine. It's pretty straight forward.

 

[plonk420]

ah, cool! thanks for the extensive post! guess i'll have to run in test driver mode after all, if i want high res screenshots.

2880x1800 worked at the "test this resolution" screen. i'll have to give it a try in-game!

edit: and a preliminary test works! however, it crashed when i tried to take screenshot from FRAPS... ah well. will do some more testing. and thanks again for the info!

 

[plonk420]

just wanted to follow up: updating fraps to something post-2.5.0 which i was running fixed the crash!