The Technology of GTA IV/RDR *Rage Engine*

[babcat]

The topic of this thread is to be the GRAPHICAL TECHNOLOGY used in GTA IV.

Examples could be pixel shading, geometry shading, texturing, anti aliasing, texture streaming, lighting, etc.

I'm very interested in finding out exactly what graphical methods were used in this game.

For example, it seems that Level of Detail is used. This is because objects in the distance (even a moderately short distance away) look much less detailed. Is this an LOD system or is a blur filter being used instead of AA?

 

[Neb]

Pretty much all games use LOD, it is just a mather of how 'aggressive' it is. Saves perfomance saves memory.

 

[Shifty Geezer]

LOD is used in every game AFAIK. It makes absolutely no sense to render a 10k model when it's at a distance where it's rendered as only a few pixels on the screen. If you want this thread to develop into anything, you really need to pick specific areas of technology that stand out. Otherwise you can learn the techniques GTA is using by just reading some graphics primers - it's generally the same tech used in every other game.

 

[_phil_]

plus subpixel-sized polygons cost a lot more.

 

[babcat]

Pretty much all games use LOD, it is just a mather of how 'aggressive' it is. Saves perfomance saves memory.

I think the LOD is very aggressive. Objects only thirty feet away are very blurry. Is this a blur filter or aggressive LOD?

 

[Shifty Geezer]

Blur will be a filter. LOD isn't going to affect edge blurriness. The likely explanation (not referring to any pictures here, so I'm not seeing what I'm talking about ) is LOD and a DOF blur. Which TBH is a great idea. Things at a distance can be rendered in low quality with processor savings and fuzzed out to hide the graphical simplicity while adding some artistic placement - as long as the game genre supports it. You wouldn't want that in a FPS!

 

[MazingerDUDE]

One of the best use of LOD in recent game was definately in the MLB 08 THE SHOW

The game certainly has far denser crowd than MLB 2K8, yet frame rate is so fluid.

It seems almost nonesense to see MLB 2K8's frame rate suffers terribly whenever camera shows its rather scattered crowd.

This actually reminded me of nAo saying about LOD being so important, that as long as you do proper LOD, RSX's vertex performance is sufficient enough.

THE SHOW's LOD is work of art as it's almost impossible to notice when the 3D crowd turn to 2D. (however it's easily detected at forced 1080P mode, due to higher res with shorter LOD distance :smile

 

[betan]

Pretty much all games use LOD, it is just a mather of how 'aggressive' it is. Saves perfomance saves memory.

I'd think LOD costs memory more often than not.
So most of the time, it should be a trade off between memory and speed.

THE SHOW's LOD is work of art as it's almost impossible to notice when the 3D crowd turn to 2D. (however it's easily detected at forced 1080P mode, due to higher res with shorter LOD distance :smile

It's also very easy to detect in replay mode, when approaching the crowd from weird angles.
Still great game visually.

 

[Simon F]

I'd think LOD costs memory more often than not.
So most of the time, it should be a trade off between memory and speed.

And aliasing!

 

[assen]

I'd think LOD costs memory more often than not.

Depending on the streaming system - I would guess a game like GTA4 keeps only low LOD of the skypscrapers 200 m down the street in memory.

 

[Hazuki Ryu]

plus subpixel-sized polygons cost a lot more.

Never hear that before interesting would you care to explain why?

 

[AlNom]

Never hear that before interesting would you care to explain why?

Laa-Yosh had a nice post on it:
http://forum.beyond3d.com/showpost.php?p=791449&postcount=2
edit:
And another
http://forum.beyond3d.com/showpost.php?p=604793&postcount=73

 

[digitalwanderer]

I JUST NEED IT TO COME OUT FOR PC RIGHT NOW!!!!

Sorry, sorry...it just slipped out.

 

[Laa-Yosh]

...

Also, today's GPUs are shading 4 pixels at a time, and rasterize the geometry by polygons. So if a polygon is smaller than 4 pixels then the efficiency of the pipeline starts to drop. If the polygon is smaller than a single pixel, it's a loss of 75%, you basically cut your speed to a quarter.

Multisample AA (more zixels per pixel) may change things a bit but I'm too tired to think it through

 

[babcat]

Please look at these two images. Do you see how blurry the objects become? You cannot even see the faces of certain characters. Also, cars become extremely blurry.

Is this due to a filter, DOF, or what?

 

[AlNom]

For the characters, you're seeing the effect of very aggressive LOD. In the second shot, it looks like some sort of atmospheric shader of sorts (or maybe just bloom) plus incredibly noisy shadowing.

Oh and there's also the IGN filter, which entails crappy compression.

 

[Shifty Geezer]

Looks to me like there's a paint-type post effect, something along the lines of a median filter. There's a lot of crazy that I don't know is due to IGN's compression or deliberately pixel displacement as part of the filter effect. I'm thinking some randomizing of the pixels followed by a median filter would produce the artistic style here. I haven't got my graphics plugin stuff installed on this PC or I'd give it a try. Laa-Yosh can probably weigh in and tell me how wrong I am

Edit - I'll just add that I know a median on it's own wouldn't get the exact look. You'd need to localise it to within objects. Looking at the checkered dithering though which appears localised to certain noisy materials, specifically the trees, and around object edges, I'm pretty confident that's what's going on. Reminds me of a very early XB360 screenshot from an ant game, where everything was dithered to betsy, and this was a DOF pixel redistribution without the blur filter.

 

[TimothyFarrar]

I'd place my bet that they are doing doing a combination of a screen space motion blur and screen space dithering (looks a lot like non-linear filtering like median) all in one pass. A lot like what I was talking about in one of my previous blog entries,

"For those who have normal stored in their G-Buffer, here is an idea on how you can get really high quality anti-aliasing with a image space post process, without using hardware anti-aliasing. First take the per pixel normal, project into screen space, and re-normalize. Then take this screen space normal, and rotate 90 degrees (compute the vector perpendicular to the screen space normal). This perpendicular vector will be in the direction of the strongest "edge" at the pixel. Now like screen space motion blur, sample from the screen in the direction of this perpendicular vector, and intellegently (ie look at depth) take a weighted average of a few screen samples along both the positive and negative directions on this vector. Would have to workout the details, but the concept should work really well."

From other screen shots it looks as if this filtering pass is done prior to the depth of field pass, and prior to the bloom pass.

 

[Laa-Yosh]

I'm not that much into the 2D part, and this one looks like such an effect. I really wonder how it'd look on a regular LCD TV, and how it would look on a plasma - there'd probably be some difference...

 

[AlNom]

Why would there be a difference between LCD and Plasma

...

When does the AA not work? I've noticed during the latest trailer that there are several edges that don't get any edge AA, and it almost always seems to be the case when an object is against a distant background i.e. the sky.