*Sub-Thread* Dithering in GTA4

[Shifty Geezer]

I dont' follow you as to why mipmapping is excluded. It looks like the screenshots with magnification are fine, but as it transistions to the first mipmap (beginning at 2 pixels per texel, here), the text slowly starts getting more messed up until the base level isn't there anymore.

What I meant was the problem isn't just a matter of the mipmap images being corrupted. The increasing amount of distortion with distance isn't a gradual blending between a clear image and a noisy image, but the increasing introduction of more distortion. Where ordinary mipmapping LERPs two images and a texel is m% image 1 : n% image 2, in this case it's as though a texel is either 100% one or other image, and the percentage of pixels of the second image increases over distance. Kinda like a primitive mipmap blending - if you didn't have interpolation available, you could mix pixels from two textures

If Rockstar is creating the mipmaps at runtime using their own code, they could be writing into memory incorrectly, locally swapping texels.

That would explain the slight offsets we're seeing, misaligned memory.

 

[MazingerDUDE]

Try downscaling this to 853x480:
http://dot50cal.the-horror.com/b3d/gta4/dithering/x3-image19.png

It doesn't look any different from this:
http://dot50cal.the-horror.com/b3d/gta4/480p/x3-image33.png

Actually it does

* I did downscale using photoshop


480P is still a bit more clearer

It's even more staggering to find out that, 720P actually provides less detail than 480P

 

[Mintmaster]

480P is still a bit more clearer

It's even more staggering to find out that, 720P actually provides less detail than 480P

There's barely any difference there. It could just be where the exact texture coordinates positions happen to fall, the weights of the bilinear sampling, and the lancoz filter used by 360. There are some places where your first image has better detail than the second, like the burger image, "B", "u", and tails of the "S".

Look at the neon lights. The 480p matches the 720p downscale. Heck, look anywhere. You're splitting hairs here.

 

[MazingerDUDE]

There's barely any difference there. It could just be where the exact texture coordinates positions happen to fall, the weights of the bilinear sampling, and the lancoz filter used by 360. There are some places where your first image has better detail than the second, like the burger image, "B", "u", and tails of the "S".

Look at the neon lights. The 480p matches the 720p downscale. Heck, look anywhere. You're splitting hairs here.

Just added another 400% shot with 480P upscaled to 720P

I believe the difference is way too obvious to be just ignored.

The dithering effect destroyed texture quality almost down to sub 480P level.

 

[Mintmaster]

What I meant was the problem isn't just a matter of the mipmap images being corrupted. The increasing amount of distortion with distance isn't a gradual blending between a clear image and a noisy image, but the increasing introduction of more distortion. Where ordinary mipmapping LERPs two images and a texel is m% image 1 : n% image 2, in this case it's as though a texel is either 100% one or other image, and the percentage of pixels of the second image increases over distance. Kinda like a primitive mipmap blending - if you didn't have interpolation available, you could mix pixels from two textures

Are you sure that's how this artifact behaves? It doesn't look like it to me. I think it's a gradual blend. Look at these crops, and keep in mind variance from texture coordinates and bilinear filtering:

 

[B1663r]

Mintmaster,

My only point was that the artifacts are less distracting at 480p. Less boiling in the sunlit shadows, the edges look smoother, etc etc. Overall, the game looks more like the title screens and box art, IMO.

 

[Mintmaster]

Just added another 400% shot with 480P upscaled to 720P

If you upscale your downscaled 720p image, it will also look better than the original 720p image. You're not proving anything and just misleading people.

Try scaling the 480p BurgerShot sign down to the size of the smaller one right next to it. It will look better, because that smaller sign is blurred from the dithering of when it was rendered at 720p.

BTW, did you look at the neon edges yet? It's blatantly obvious that the 480p image is downscaled from 720p.

 

[Colourless]

Could this still be some mulitsampling AA hack. Maybe they are rendering using 4X aa at half the resolution and then displaying as 2X at double?

 

[Mintmaster]

Mintmaster,

My only point was that the artifacts are less distracting at 480p. Less boiling in the sunlit shadows, the edges look smoother, etc etc. Overall, the game looks more like the title screens and box art, IMO.

I totally understand that. I'm just trying to point out that it's nothing more than a downscaled version of the original image.

The shadows are definately the biggest source of dithering. Rockstar really didn't try very hard on the 360 version. They got 720p with 2xAA and completely ignored this obvious texturing bug, ignored 360 specific features life fetch4, possibly used alpha blending on PS3 for trees/fences but alpha-to-coverage on the 360 version, and tweaked the light color on the PS3 version to a "warmer" tone that people like but forgot to do the same on 360.

 

[Mintmaster]

Could this still be some mulitsampling AA hack. Maybe they are rendering using 4X aa at half the resolution and then displaying as 2X at double?

Nah, we've seen devs do similar things before and there are obvious visual cues. Either horizonal or vertical edges will have alternating light-dark sequences. Interiors of polygons will have pairs of identical pixels due to the same pixel shader result for all samples. It's very clearly 720p with 2xAA.

 

[MazingerDUDE]

I'm just trying to point out that it's nothing more than a downscaled version of the original image.

Just added another 400% shot

If you still think they are the same, I got nothing more to say

 

[B1663r]

Any big business graphics developers here? Or just art critics? I know when Microsoft was developing WMA audio compression they made extensive use if ABX testing to determine if their build was actually improving the thing, or if it was making things worse. Would any sort of objective QA test like this be performed on game graphics? If so, with news reports that this game cost 100 million+ dollars to develop, what could happen to derail that process in this game?

 

[Mintmaster]

Just added another 400% shot

If you still think they are the same, I got nothing more to say

So? Don't you agree that the downscaled and then upscaled looks better than the original? That was my point. You were making a useless comparison with the first two.

Look at what you're starting with in the 720p image. Shift the view by a quarter pixel, and you get different data to scale. Do you know what alternating black and white stripes in a texture on the screen looks like when shifted by half a pixel? Just plain grey.

You have not shown me any conclusive evidence of more detail. It was just a fluke that one is the tiniest bit less clear. Look at this shot:
http://dot50cal.the-horror.com/b3d/gta4/480p/x3-image35.png
Compare it to this downscaled:
http://dot50cal.the-horror.com/b3d/gta4/dithering/x3-image21.png

They're virtually identical, with no difference in detail whatsoever. The neon signs have identical step patterns.

 

[MazingerDUDE]

So? Don't you agree that the downscaled and then upscaled looks better than the original? That was my point. You were making a useless comparison with the first two.

Not really

While the 720P shot is a lot sharper, the upscaled 480P shot is blurred yet contains more information.

The downscaled and then upscaled 720P is just blurred with same level of information as 720P

I wouldn't call that 'better looking'

 

[Mintmaster]

Not really

While the 720P shot is a lot sharper, the upscaled 480P shot is blurred yet contains more information.

No it doesn't. That one tiny part of the screenshot has marginally more information by chance. I'm sure I could find the opposite somewhere else.

Why do you keep ignoring everything else in all my other posts?

Enough of this. The 480p setting is just 720p downscaled and contains no more information. We have gobs of proof, and if you won't accept it then that's fine. Just stop going on about it.

 

[Betanumerical]

Can you tell what Fable 2 is running at?

http://kotaku.com/assets/images/kotaku/2008/05/F2_house_1280.jpg
http://community.lionhead.com/photos/fable2_photos/images/2907781/original.aspx

Whats up with the odd looking leaves to right of the house in the first shot.

 

[Jesus2006]

Whats up with the odd looking leaves to right of the house in the first shot.

Looks like dithering to me.

 

[betan]

Looks like dithering to me.

Yeah it looks like dithering to emulate alpha.
Maybe a flag left on after rendering print copies.

Very beautiful game though.

 

[betan]

I'm not even sure why a decal is used instead of a texture for that small object,

It looks like it's being reused quite a lot, and the little displacement gives nice 3d depth.

 

[fozzy600]

hello everyone

I'm playing gta4 on a 1080p display via hdmi on my 360 elite and I'm guessing that because the internal upscaler is re-sampling the image. I'm not seeing the same level of iq issues. IMO this game looks spectacular given its scale and considering the fact that its streamed off disc on the fly.