*Sub-Thread* Dithering in GTA4

[B1663r]

Pugger,

The boiling and moire patters at the side of shadows and in car grills drag your eye away from whatever you were trying to focus on, on the xbox version at 720p. However at 480p the blurryness all seems to go away, the DOF seems... more natural, and that boiling effect at the side of shadows on sunny days is much reduced. But then it is in fatso vision...

 

[Mintmaster]

Why do you think it has transparency inside the font?
I could understand the outline, but inside? Does it give better results when texels are small or something?

I have no idea, as I'm just guessing. Maybe an artist was thinking about making it glow or something, and that would be easier with the GTA engine and its standard shader set if they just made the sign underneath change brightness. Sort of like a real sign.

I'm not even sure why a decal is used instead of a texture for that small object, but sometimes when you give an artist too much freedom he/she doesn't really care about which method is used as long as the job gets done.

Remember, this is all a theory. It's the other screenshots where dithering affected things that are clearly a decal that made me think this BurgerShot sign is also one.

 

[Mintmaster]

Hello everyone. Shifty pmed me asking for some shots, so here you all are. I took many shots so I hope they are of some use. I can take more if needed. I was particularly interested in the building shots. The red brick seems to have the same effect on it until you are very close to it. So this seems to affect all textures??

I missed your post. Thanks for the shots.

I still think it has something to do with the decals, but I'm not too sure about my explanation now with the alpha to coverage. The zoomed in sign looks fine. Maybe there's something wrong with the mipmap generation, causing trouble only with minification. For grass, trees, and fences, alpha-to-coverage still makes sense.

 

[Dot50Cal]

Here are some 480p shots, as requested. The game appears to be rendering in HD, and scaling down (look at the neon lines that weren't anti-aliased in 720p).

http://dot50cal.the-horror.com/b3d/gta4/480p

 

[MazingerDUDE]

I don't have capture device, so this is just a digital camera grab.

It was taken from PS3 hooked to monitor via HDMI to DVI with 1:1 pixel matching at 720P

The photo was just resized, no additional sharpen filter added


http://dot50cal.the-horror.com/b3d/gta4/dithering/x3-image25.png

Even with this blurred & darkened camera shot, it shows more details on all these signs

Seems like even at the lower res of 640P, PS3 version actually shows more details, especially on textures

 

[liolio]

First thanks to the devs hare and Dot50cal who always go through a lot of efforts to enlight us with technical insight.

Second point, It looks like the game should have been delayed in regard to some bugs...
So I think it's clear that the game will be patch sooner than latter (between bad new for arcade owners...)
Mintmaster by reading your comments I feel like Fixing some of the IQ problems on the 360 would be trivial (like desactivating some effect at driver level).
Would it be possible that the likely up coming patch could easily improve IQ on both versions?

 

[Sc4freak]

I don't have capture device, so this is just a digital camera grab.

It was taken from PS3 hooked to monitor via HDMI to DVI with 1:1 pixel matching at 720P

The photo was just resized, no additional sharpen filter added

[snip]

Even with this blurred & darkened camera shot, it shows more details on all these signs

Seems like even at the lower res of 640P, PS3 version actually shows more details, especially on textures

That's hardly a valid analysis. Given the very low quality of a shaky-cam shot, it's impossible to draw any sort of conclusion based on that evidence alone.

 

[Dot50Cal]

Please dont display shots hosted on my webserver, especially if they are 1MB PNG files.... Can a moderator please edit his post so its a link and not a display?

 

[AlNom]

Done.


Just a friendly reminder to all: Please do not use img tags for images or direct links to video downloads from non-free hosting websites. Either rehost the image or video, or link to the accompanying news/media/gaming website where the link may be found.

 

[Shifty Geezer]

Hello everyone. Shifty pmed me asking for some shots, so here you all are. I took many shots so I hope they are of some use.

Many thanks!

I can take more if needed. I was particularly interested in the building shots. The red brick seems to have the same effect on it until you are very close to it. So this seems to affect all textures??

I'm seeing two different effects - dithering and noise. They may be related, but I'm definitely seeing a difference in the dots. On the wall, and indeed throughout all the external images, there's dithering everywhere, and by that I mean proper dithering with regular patterns. On the indoor pics, most of the scenery is clean and dither free, but with some surfaces having noise that isn't regular dithering.

I'll just showcase a couple of examples of the difference between dither and noise for those who aren't sure. This is the PS3 sign :

This is the same image brightened to match the XB360 example and dithered with 64 and 16 colours using a weak algorithm :

Compare these with the XB360 example

Look at the 'e' above or the tail of the 'S' and you can see the noise there is destructive. The amount of colours present in that logo is sufficient to preserve the structure of the text well if it were using correct dithering, but it's not. Dot50Cal's images show this noise is progressive over distance, so can't be a matter of mipmap creation unless they aren't using trilinear filtering and they're point-sampling a noisy or offset texture.

But the really bizarre thing is the noise isn't confined to textures, but rears it's ugly head in a strange combination of geometry. Looking at the pink and green neons on the right, the edges are mostly well structured except where the electrical wiring passes behind them. Then there's an area of a few pixels radius where the neon colour 'runs' into the scenery. This suggests a post effect.

I'm wondering if there's an attribute being used in post as part of the art effect, that's getting muddled in some situations of overlapping/adjacent values. Perhaps a multipass rendering system is blending elements at the wrong point?

 

[Jesus2006]

But the really bizarre thing is the noise isn't confined to textures, but rears it's ugly head in a strange combination of geometry. Looking at the pink and green neons on the right, the edges are mostly well structured except where the electrical wiring passes behind them. Then there's an area of a few pixels radius where the neon colour 'runs' into the scenery. This suggests a post effect.

The noise is also apparent in peoples faces and hands (polygons?) in dot50s shots. On 360 you can't even determine the faces of some NPCs correctly because of this dithering.

Could it [dithering] be used to hide a lower color-depth used for the DoF effects? I know there shouldn't be DoF in this very scene but i noticed at least on PS3 the DoF kicks in even if it's not needed sometimes (e.g. in some cutscenes, which is also why some people find the PS3 version more blurry).

 

[B1663r]

Jesus2006,

For me, the problem with the dithering is minimal. Where I am having trouble with the graphics is the boiling of the shadows on bright days, and the moire pattern in the grill of the cars, the still images just don't convey how distracting they are. It is like the optical illusion tricks... It pulls your eyes away from where you want to look. For me the effect on a 42inch tv from about 5 feet away is motion sickness inducing.

I am sticking with playing the game in 480p for now, because that seems to really minimize the issue. (and the motion sickness is gone) I wonder if we will see a patch that lowers the resolution of the 360 version, because I think that is a partial solution.

Also at 720p playing the game while the sun is in the sky, with those boiling shadows is very fatiguing on the eyes.

1080i also seems to reduce the effect... but not as much as 480p.

 

[liolio]

High first post

Wow, could someone else with an xbox lower the console resolution to 480p and tell me what you think? On the xbox at least, I have to think this looks more like what Rockstar had in mind when they designed the game.

Interestingly, the one with a 1080p display could tell us if there a diiference on the 360 version (out of curiosity).

 

[MazingerDUDE]

It's intereting to see how 480P captures have zero ditherings

following 400% shots were taken from

http://dot50cal.the-horror.com/b3d/gta4/480p/x3-image33.png
http://dot50cal.the-horror.com/b3d/gta4/dithering/x3-image25.png

(I apologize Dot50Cal for the direct link )

 

[B1663r]

Is it me are are there 4 color graduations in the 480p edges and only 2 color graduations in the 720p version?

 

[Jesus2006]

Is it me are are there 4 color graduations in the 480p edges and only 2 color graduations in the 720p version?

2x vs 4x MSAA?

 

[Mintmaster]

Look at the 'e' above or the tail of the 'S' and you can see the noise there is destructive. The amount of colours present in that logo is sufficient to preserve the structure of the text well if it were using correct dithering, but it's not. Dot50Cal's images show this noise is progressive over distance, so can't be a matter of mipmap creation unless they aren't using trilinear filtering and they're point-sampling a noisy or offset texture.

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. Also note that each BurgerShot sign, regardless of orientation, shows the text degrading in the same way (like here).

One reason that this could happen is an incorrect data tiling setting or assumption by Rockstar. in the memory. The textures aren't stored line by line like a BMP, but rather one 2x2 tile at a time, and sometimes these are then macrotiled. If Rockstar is creating the mipmaps at runtime using their own code, they could be writing into memory incorrectly, locally swapping texels.

It really does look like you only see the problem when the second level mipmap starts blending in.

But the really bizarre thing is the noise isn't confined to textures, but rears it's ugly head in a strange combination of geometry. Looking at the pink and green neons on the right, the edges are mostly well structured except where the electrical wiring passes behind them. Then there's an area of a few pixels radius where the neon colour 'runs' into the scenery. This suggests a post effect.

That doesn't look like the same effect at all to me. You're probably right in suggesting that the post-processing is responsible for this, but it's not dithering.

 

[Jesus2006]

That doesn't look like the same effect at all to me. You're probably right in suggesting that the post-processing is responsible for this, but it's not dithering.

For me it does. Also the 720p screenshot here seems to have the same dithering artefacts inside the face geometry (look at the nose or ears):

http://www3.telus.net/public/dhwag/2.jpg

Of course the contrast is lower here so it's hardly noticable in this case but compared to a 480p shot something is definatley there.

 

[Mintmaster]

2x vs 4x MSAA?

The Neon lights suggest downscaling from 720p (i.e. supersampling), because 2x multisampling doesn't do anything to them when 720p is the output resolution.

For me it does. Also the 720p screenshot here seems to have the same dithering artefacts inside the face geometry (look at the nose or ears):

http://www3.telus.net/public/dhwag/2.jpg

Yeah, but that could just as well be textures on the geometry doing the same thing as the BurgerShot sign. Anything that isn't textured doesn't get affected.

You have to realize that in the 480p screenshots the were rendered 1.5x bigger in each direction and then downscaled. We already know that the 720p image is fine for larger objects.

 

[Mintmaster]

It's intereting to see how 480P captures have zero ditherings

following 400% shots were taken from

http://dot50cal.the-horror.com/b3d/gta4/480p/x3-image33.png
http://dot50cal.the-horror.com/b3d/gta4/dithering/x3-image25.png

At first it looked like a stunning difference, but you have to realize having equal sized objects in the crops does not mean equal sized objects on the screen. The first pic, had it been rendered at 720p, would have been drawn much larger, like in this pic. We only see the back of his head, but there's no evidence of dithering around the ear or anything like that.

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

The 480p "improvement" is just a red herring. GTA is rendering at 720p as usual and the 360 is downscaling.