nVIDIA's New GeForce4 Ti and GeForce4 MX
The NV25 and NV17 Debut

By Dave Altavilla
2/6/02

  
Well as we all know, the jagged edges of a heavily aliased scene, certainly do take away from the realism of any 3D image.  The GeForce4 was targeted to breath new life into real-time Anti-Aliasing and NVIDIA believes you shouldn't have to turn it off in order to have acceptable frame rates for certain games.  We'll take a look at NVIDIA's Accuview next.

GeForce4 Accuview Anti-aliasing
Getting rid of the "jaggies" while sustaining great frame rate - "Just leave it on"

With the GeForce 4 and GeForce 4MX, NVIDIA has incorporated more efficient, patent pending, Anti-aliasing logic which they have dubbed "Accuview AA".  Prior to the release of the GeForce 3, NVIDIA used super-sampling to help remove the "jaggies" from an image.  To put things simply, what super-sampling does is render a given frame at a higher resolution, 2X or 4X the native resolution for example.  Then, from the higher resolution frame, color samples are taken from around each pixel, the colors are blended together and then that frame is scaled back down to the native resolution. Because the original frame is rendered multiple times, super-sampling requires large amounts of memory bandwidth and fill-rate to handle all of the duplicate texture and vertex data.  So while visually, super-sampling AA does produce excellent images, the performance hit is substantial and not feasible on most GPUs at any native resolution over 800x600.  This is why NVIDIA incorporated logic into the GeForce 3 to perform a different AA method known as multisampling.
 


Vastly simplified, multisampling works in a similar fashion to super-sampling, but due to the "features" incorporated into the GPU, the original texture data is not sent through the pipeline multiple times.  Because the texture data is reused, far less memory bandwidth is required to enable Anti-aliasing.  The existing texture data is used to take color samples from "virtual pixels" surrounding the original pixel, and then all of the color samples are blended together.  Multisampling has a few side effects though.  Since less bandwidth is required, performance is increased but at the expense of image quality.  When using multisampling, because the texture color data is reused, textures generally get blurred.  To combat this blurring effect, a variety of techniques can be used, like Anisotropic filtering, or changing the location of the "virtual pixels" used for the color samples.
 


Depending on which AA mode is chosen, Accuview AA uses both of these methods to increase visual quality, and due to architectural optimizations, performance is increased as well.  NVIDIA claims the GeForce 4 can do AA twice as fast as the GeForce 3, because the architectural enhancements save an entire frame buffer write.  A new AA mode, "4xs", has also been introduced which uses new sample positions and texture sharpening for a new level of AA quality previously unavailable on other cards.

Let's have a look at some in game shots at the various settings.

GeForce4 Ti 4600 and GeForce4 MX 460 Benchmark and Performance Update
2/10/02

 

Accuview in Action - Novalogic's Comanche 4:

Alright, I'll admit it.  Not everyone is a Flight Sim or Combat Flight Sim fan.  However, in the age of the "first person shooter", I felt compelled to give you eye candy from behind something a little more interesting that a rocket launcher or rail gun.  Not that you could fall asleep with either of those but you get my drift.  So we took to the skies with Novalogic's great looking new Combat Chopper Sim, Comanche 4.  This game looks fantastic and is a blast to play.  It is a DirectX 8 title with full support for vertex and pixel shaders.

2X AA

Quincunx AA

4X AA

4XS

 Eye Candy 1

Eye Candy 2

Eye Candy 3

First some observations... We had a bear of a time getting screenshots with Hypersnap, our usual method.  When in AA mode, it just kept grabbing captures of an entirely different screen in the game than we were trying to capture at the time.  So, we had to trust the built in screen capture capabilities of Comanche 4.  Frankly, we're waiting to hear back from NV and Novalogic as to whether or not the above screenshots are representative of the AA settings they were taken in.  However, take a look at the 2X shot, it still has a fair amount of jaggies going on.  We took all shots at a 1024X768 resolution.  Then compare Quincunx mode versus 4X and 4XS mode.  You will notice that the textures for the ground look a lot better in 4XS mode versus Quincunx and even slightly better than 4X mode.  Versus 4X mode, the effect is very subtle however.  Regardless, on the GeForce4 Ti 4600, this game is simply amazing and with full 4X AA, totally smooth.  The rest of the shots were taken with 4X AA and are there for just gazing at.  Very nice indeed.

Alright then, I think we've covered most of the new features and salient points of NVIDIA's new GeForce4 architecture.  Let's have a look at the drivers and a few initial tests.

The benchmarks are next!

New Detonator 27.30 Drivers and Quake 3 Scores