



A difference map of the two images







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RE: wow
By defter on 7/19/2006 6:34:18 AM , Rating: 2
In this case it was very easy to see that it was Photoshopped.

1. There were clear sharpening artifacts in "ATI screenshot" image
2. There were two images, thus it was very easy to compare them and see the differences.

I see this site is full of graphics experts...
By Justin Case on 7/19/06, Rating: 0
By glennpratt on 7/19/2006 9:46:42 PM , Rating: 2
I think the difference map was used to point out that it looks like the difference was something along the lines of a photoshop blur tool, rather then a totally different video card. But who knows.

RE: I see this site is full of graphics experts...
By Knish on 7/20/2006 2:07:05 AM , Rating: 2
Actually, you don't know what you're talking about. I'm sorry.

Image compression at diferent levels will produce different sampling, which would be very evident in a difference map. As many others have pointed out, the difference map seems to indicate the boundaries of the photoshop. Please explain to me why only the water shows a difference and the rest of the image is completely static??? I mean come on, there isn't a single pixel difference in the rest of this image (I tried it myself too). Please I'd love to eat my hat if you can show me evidence of an image where such a difference map can be produced other than with photoshop. Oh and never mind the metadata, the timestamps or the fake screenshot.

I didn't even know the inquirer had fanboys until today.

By Justin Case on 7/20/2006 1:37:41 PM , Rating: 1
Do you know what a pixel shader is?

It's essentially a small program that modifies the colour of pixels. It's trivial to make a pixel shader that behaves exactly like a Photoshop (or PSP, GIMP, etc.) "sharpen" or "blur" filter. In fact, a lot of games do use such pixel shaders to simulate depth of field, Windows Vista uses it to simulate frosted glass, etc.

If a certain area of the image uses a certain shader, but other areas don't (or if they use shaders with different precisions), it's perfectly possible to get the same results on some areas, but different results in other areas.

You'll even see that in some "real" games (ex., compare a screenshot with water in Source, using two cards, a DX8.5 one and a DX9 one, and the only place where you'll see a difference is the water's edge).

Does this mean the screenshots are "genuine"? Of course not. But the fact that most people here don't seem to understand what a pixel shader is (it's not the same as "old-school" texture maps, it's a completely different concept) or how it works (pixel shaders can work in screen space, so they can even operate on pre-rendered bitmaps) doesn't mean the benchmark author's claims (that there is a difference between ATI's and nVidia's shader pipelines) is false, either.

Like I wrote before, there simply isn't enough information. If, instead of two stills with lossy compression, we had a movie, maybe we could say for sure "it's fake" or "it's real". As it is, and without knowing what exactly the benchmark is doing (for all we know it could simply be applying a shader to a pre-rendered bitmap), it's just silly to make any definitive statements.

The only way to really "discredit" the benhcmark author's claims (as this "article" purports to do), is to write a few high-precision shaders and compare the results on both cards (preferably just compare the numbers; don't bother with images). That would be a useful article.


By glennpratt on 7/20/2006 5:05:27 PM , Rating: 2
Unfortunately for you, pixel shaders don't work like a paint brush either. Take a look at the images back to back and tell me it was shaders with a strait face.

By The Cheeba on 7/20/2006 5:12:16 PM , Rating: 2
I'm fairly positive "Justin Case," who just registered after this article was published, is an inquirer employee. His comments seem to mimic what Fudo has written in his articles, and it seems very abundantly clear to most people who know what they are talking about that pixel shaders and photoshop have nothing to do with 16-bit precision, which was what these images were supposed to "prove"

Inquirer, thank you for stooping even lower than i already thought was possible.

By Justin Case on 7/20/2006 7:46:31 PM , Rating: 1
I'm fairly positive "Justin Case," who just registered after this article was published [...]

I registered over one year ago, wiseguy. Check Anandtech's forums (it's the same user DB). It seems that your tendency to jump to conclusions without knowing the facts is genetic...

By The Cheeba on 7/21/2006 5:40:02 PM , Rating: 2

So you've registered a year ago, but only made 11 comments in the past year on Dailytech, all of which were in an article about the inquirer religiously and blindly defending it. If you arne't mike magee you work for him -- but I would expect nothing less than the immaculate journalistic integrity of the inquirer.

By Justin Case on 7/20/2006 8:06:45 PM , Rating: 1
Pixel shaders, as the name implies, operate on pixels. Specifically, when applying a pixel shader to selected areas of a pre-rendered image, the shader will affect the areas defined by the mask. That mask can be based on the original material IDs, on a mathematically defined shape, or it can be a simple grayscale mask created using... a brush in a paint program.

If the benchmark author was claiming that the whole water effect was the direct product of a pixel shader, applied to a 3D scene, I'd say "bullshit". But he isn't. For all you or I know, the "pixel shader" might be running on a pre-rendered image (a 2D bitmap), based on a hand-drawn mask.

Do I think the images in question came straight out of a 3D engine? No. In fact, I'm 99.9% sure they didn't. But, AFAIK, the benchmark author never claimed that they had.

Maybe the pixel shader in question is a lot like a sharpen filter (pixel shaders can and do run on screen data, not just mapped textures), and maybe the benchmark author simply drew a basic mask to define where the shader would run.

Without more information about what the benchmark is doing (or what it's supposed to be doing), there's simply no way to tell.

Like several people have pointed out, even a five year old can follow the water's outline better than whoever drew that mask over the image (hell, Photoshop's magnetic lasso will do it automatically for you). So I think it's perfectly possible that what we're seeing as signs of a "fake" are simply signs that the "shader" was something applied to a bitmap, with a quickly-drawn mask, and not to textures mapped onto polygons on a 3D scene.

Until the benchmark author makes it clear what that image is supposed to be, both possibilities remain valid.

And none of this has anything to do with the fundamental issue of the pipeline precision. Even if the images turn out to be mock-ups made by a 4 year old, that still doesn't prove anything about the shader precision, one way or the other.

