*Sub-Thread* Dithering in GTA4

I can confirm this, I'm playing the PS3 version at 720p (selected on xmb of course) in a 1600x1050 Samsung 226BW monitor and the shadows have dithering. I think I've only seen dithering in these shady situations (hur hur I kill myself) though.

 

i have the X360 and there are lot of dithering effect (soft shadow method + another strange effect) it's really displeasing like "lot of aliasing"

 

Upscaling tends to make dither patterns more obvious, not less (try it with any number of various PS2/GC/Wii/PSP/PS1/DC etc.) games on a HDTV.

Blurring could do it though - if there's something like that really going on. Though people in this thread seem to suggest otherwise.

 

Not really. It depends on whether you upscale with bicubic or bilinear filtering. Both of those methods tend to diminish the dithering. I took the compare screenshot I took of the 360 and resized it to 1920x1080 using both bilinear and bicubic, and both of them made the effect of dithering less apparent.

 

Here's another set of 400% shots

taken from these images

http://imk.cx/screenshots/xbox360/Grand Theft Auto IV/compare.png
http://img294.imageshack.us/img294/4913/wmplayer200804280036497sh8.png







I doubt any blur filter can create details that simply don't exist.

 

If top is 360's version - why is it looking looking so jaggy comparing to PS3's version where the resolution is lower?
Bottom picture is clearer but how could it be? 640p better then 720p? Or else?

 

I felt the 360 version looked cleaner (for example the top of the stairs, Niko's hand, Niko overall etc). Changing the image ratios to give the 360 version a darker more contrasted look may also change one's interpretation of the pics.

 

the visual problem of the X360 version is in movement (like shimmering or other similar artifact), not really in screenshot

 

No argument here. The X360 looks certainly cleaner. But I think Sam is referring to the zoomed out portions of the pic. Here the cleaner look is due to the blur filter blurring out the color differences, thus looking better to the human eye / brain. Our brain has an easier time coping with "noiseless" visual information. Thus giving the zoomed PS3 pic a cleaner look even though the information content is lower in that screenshot (i.e. 640p vs. 720p).

Sam, if you want do a little experiment you can blur the X360 image and you'll see that the sign becomes more legible.

 

StefanS is right, I refered to the zoomed out portions.
So can we say that blur filter "hides" the lower resolution of PS3's version ?

 

The PS3 image is not the XB360 with filtering applied. The noise is destructive to the character shapes. You can't recreate the smooth letters in the PS3 version from the noisy XB360 version. It looks almost like a bug in mipmapping, affecting only (small?) textures (at distance). Polygon edges remain well defined. So what'll cause noisy texturing? Poor sampling of larger textures for one. Or, it's AA samples that haven't been combined properly, the intensity of one sample with disregard for another.

Very strange.

 

You're right. I didn't look too closely at the big screen. But as you said it's fairly visible, especially if you squint your eyes.

 

The Squint test - best visual analysis tool mankind has!

Taking another peak, I'm being drawn more towards the idea of an AA resolution artefact type thing. The noise is an offset of 1 pixel from the primary surface. eg. Around the pink and green neons, you can see what look clearly like multisampled points offset from the otherwise non-antialiased edge.

 

Rockstar is using a subtle depth of field effect from what I can see. Imagine if you had a camera but focussed on the car/person (and didn't have a tiny aperture).

They were going for a cinematic look, but the problem is that directors know exactly where they want people to look at when making a movie, but a game has no idea what you're looking at. DoF looks good, but it interferes with gameplay.

Without DoF, the differences between 720p and 640p would be more apparent, but it definately gives GTA4 its own look.

 

Sorry, a little OT, but I always thought "knowing what the viewer is looking at" is the exact opposite of DoF's purpose (in movies and games). The point of DoF is to give directors and artistst the power to steer/direct the viewer's attention to the desired location no? I notice the DoF used in GTA4 tries to steer your attention towards the immediate area surrounding Niko (whether in the car, on foot, or in cutscenes), which is also where they focus the brunt of the graphics.

After spending hours and hours with the game, I've "learned" to focus where the DoF wants me to... because otherwise I'd get a headache from the DoF and LoD.

 

As I stated two pages back, I agree with Mint, that it's a DOF effect. IMO, the dithering is a result of using FP10 where you are limited to having only 2-bit in the alpha channel.

 

That's a really bizarre artifact. I can't think of much that would cause this. Maybe a crappy texture compression tool? That doesn't jive with the fact that this dithering is always at the pixel level. Even stranger is how there's not rhyme or reason as to where the dithering happens.

It's almost like we're seeing some undersampled, jittered image sampling in a post-process. Again, does anyone see this in motion in areas that aren't shadowed?

 

Could compression using ATI2N or 3Dc+ be the cause (I don't know if the sign is normal mapped)? IIRC, at least in the latter format, there would be poor artifacting with high curvature.

 

Why are only certain textures being affected, and why are they being alpha-blended? Why is the range of noise only two pixels yet the blur filter isn't that pronounced. There's no DOF causing this. Look at this pic -
http://imk.cx/screenshots/xbox360/Grand Theft Auto IV/compare.png
The geometry at the same distance as the noisy burger signs has no blurring on its edges. It's not DOF or any other blur artefact as I can see, as that pic shows no blurring, nor bloom.

 

I never said that the dithering was a DoF effect, just that the blurred look is.

2-bit alpha should not affect DoF, as that effect doesn't need destination alpha. Almost nothing does.