X1800/7800gt AA comparisons

[Xmas]

So if the GPU renders in sRGB colorspace (gamma = 2.2), shouldn't the driver be able to apply an ICC correction post-process?

If it does... but I don't know any game that cares about using the right color space. Besides, there's no sRGB blending yet.

 

[FX5900]

nvidia>Ati from what I'm seeing

 

[DemoCoder]

If it does... but I don't know any game that cares about using the right color space. Besides, there's no sRGB blending yet.

IIRC, DX9 added support for sRGB texture formats, and sRGB render targets. Wouldn't that indicate that blending occurs in sRGB space?

I'm actually interested which DirectX drivers make any use of the ICC profile for the front buffer. It seems if they allow gamma ramp modification, they should support colorspace conversion. NVidia drivers I know support it, you can go to the color correction screen and "import" any ICC profile you which.

 

[vember]

IIRC, DX9 added support for sRGB texture formats, and sRGB render targets. Wouldn't that indicate that blending occurs in sRGB space?

Yes, and that's exact what we want to avoid. Historically, textures and framebuffers have always been in sRGB format (roughly), but they were treated as if they were linear data. The new thing in DX9 that you mention is that it allows conversion of texture reads (sRGB->linear) and pixelshader outputs from (linear->sRGB) so you can do linear processing in the pixel-shader on linear data, even when your textures and framebuffers are in sRGB.

It is possible to use a linear space framebuffer and do the conversion back to sRGB space post-blending. The dealbreaker is that 8-bits/channel isn't nearly enough presicion to get a decent image when using linear space, there's a lot of banding among darker colors. And as we all know there wasn't any blending & multisample support for higher bit-depth framebuffers available until recently.

 

[DemoCoder]

Still, I think this is orthogonal to the issue as to whether the driver can apply an ICC profile correction before scanout of the framebuffer. All it needs to know is that the framebuffer is in sRGB space and the ICC profile of the display device. Drivers already allow gamma ramp tweaking.

 

[Xmas]

IIRC, DX9 added support for sRGB texture formats, and sRGB render targets. Wouldn't that indicate that blending occurs in sRGB space?

The problem is that, AFAIK, every hardware that supports those formats still does filtering and blending in non-linear color space. So instead of linearizing texels before filtering, it happens after filtering (so filtering does linear math with sRGB colors - bad). Same for blending: framebuffer writes do a conversion from linear to sRGB, however framebuffer reads don't do the reverse. So you blend a color in linear color space with a destination color in sRGB color space, then convert the result from linear to sRGB space.

And which game actually uses those flags?

 

[sonix666]

I do have to add that personally I think in some situations my Radeon X800 Pro over-gamma-corrects with FSAA. Sometimes the anti-aliased samples are all really light that 4x FSAA just doesn't look like it is on. I always did prefer the 'darker' look of nVidia (it's subjective probably), but ATi did have better sample positions up until Geforce 6800 (or was it FX already?).

 

[Pete]

GF6 series was the first to change 4xMS to rotated/jittered grid. 2xMS was always rotated grid for nV, IIRC.

 

[Moloch]

GF6 series was the first to change 4xMS to rotated/jittered grid. 2xMS was always rotated grid for nV, IIRC.

Why is it that 2x fsaa for nvidia even with the 6X series and 7XXX is completely outclassed by ati's 2x fsaa?

 

[trinibwoy]

Why is it that 2x fsaa for nvidia even with the 6X series and 7XXX is completely outclassed by ati's 2x fsaa?

Huh? Completely outclassed? A bit heavy on the hyperbole there don't you think

 

[Moloch]

Huh? Completely outclassed? A bit heavy on the hyperbole there don't you think

Not all all

 

[Pete]

Why is it that 2x fsaa for nvidia even with the 6X series and 7XXX is completely outclassed by ati's 2x fsaa?

Gamma-correction/adjustment, I suppose. Dunno about "completely outclassed," but GC helps (especially/mostly with CRTs, per Nite Hawk's recent thread).

 

[Moloch]

Gamma-correction/adjustment, I suppose. Dunno about "completely outclassed," but GC helps (especially/mostly with CRTs, per Nite Hawk's recent thread).

I posted in that thread
With my old hp 19" crt there is simply no comparison even at 4x fsaa, but it's most apparent at 2x fsaa.

 

[neliz]

I posted in that thread
With my old hp 19" crt there is simply no comparison even at 4x fsaa, but it's most apparent at 2x fsaa.

as long as you have crt, ati's AA is the way to go.

 

[Moloch]

as long as you have crt, ati's AA is the way to go.

And as long as you're interested in the best gaming/multimedia quality, crt is the way to go.

For now atleast.

 

[no-X]

Here are some pictures for better comparision:

(ATi R3xx/4xx/5xx vs NV4x/G7x)

ATi 2x / nV 2x

ATi 4x / nV 4x

ATi 6x / nV 8x

ATi should provide custom settings for AA gamma correction (at least CRT/LCD preset) to enhance AA efficiency for LCD users. Btw. which gamma correction value would be best for LCDs?

 

[neliz]

Great post no-x.. and yes. .did you fill in a bug-report sheet yet?

btw, what is up with the blurred text on the geforce 8x shot? the word ANIMATION only has IM in normal text, the rest is blurred, just like MI in MIPMAP...

nv doesn't apply AA to I's and M's?

 

[Xmas]

as long as you have crt, ati's AA is the way to go.

NVidia does have gamma-adjusted AA, too.

Btw. which gamma correction value would be best for LCDs?

There's no general "best" gamma value (or rather, gamma curve), each display is different.

Great post no-x.. and yes. .did you fill in a bug-report sheet yet?

btw, what is up with the blurred text on the geforce 8x shot? the word ANIMATION only has IM in normal text, the rest is blurred, just like MI in MIPMAP...

nv doesn't apply AA to I's and M's?

That's what you get when you have too few SSAA samples and the font texels aren't aligned to pixels.

 

[no-X]

There's no general "best" gamma value (or rather, gamma curve), each display is different.

I agree, but i mean... 2.20 is best for most CRTs (on the average). So there should be a value/gamma curve, which will be acceptable for most LCD displays.

 

[neliz]

That's what you get when you have too few SSAA samples and the font texels aren't aligned to pixels.

At 8xSSAA?