NVIDIA GeForce 2 GTS

Full Scene Anti-Aliasing

NVIDIA’s GeForce 2 GTS does support Full Scene Anti-Aliasing (for more information on FSAA read our explanation of the technology here) in hardware, but it approaches FSAA in a slightly different way than 3dfx’s T-buffer solution, which is essentially like an Accumulation buffer that any company is capable of implementing. 

NVIDIA’s FSAA works by using a method called Supersampling.  The way supersampling works is that the scene is actually rendered at a higher resolution and then scaled down to the desired resolution before being displayed.  As you already know, the higher the resolution you run at, the fewer aliasing effects are present since you have more pixels on the screen to naturally remove those effects. 

Under OpenGL applications, NVIDIA’s FSAA can work in one of three modes (much like how 3dfx’s FSAA can be run in either 2-sample or 4-sample mode).  The three FSAA settings are as follows:

·        1.5 screen resolution (lowest quality)

·        2x screen resolution, with LOD’s (MIPMaps) at the native game resolution

·        2x screen resolution with MIPMaps at the 2x resolution. (highest quality)

So if you’re running a game at 640 x 480, the first FSAA option will render the scene at 960 x 720 (640 * 1.5 x 480 * 1.5) and then scale it back down to 640 x 480 for displaying. 

Depending on who you ask (3dfx or NVIDIA) you will get varying responses as to exactly what each of these modes looks like.  3dfx will have you believe that their 4 sample FSAA looks better than all of these modes while NVIDIA will have you believe that their third FSAA setting looks the best. 

The final decision is up to you, but unfortunately, the 5.16 drivers we used for our GeForce 2 GTS tests would only allow us to enable the first setting, which renders each scene at 1.5x the screen resolution so we could only provide you with screen shots at this setting and not the other two settings.

The FSAA situation in Direct3D is a bit more flexible.  Here are the options NVIDIA’s FSAA offers in D3D:

·        2x supersampling with MIPMaps at the native game resolution

·        2x supersampling with MIPMaps at the backbuffer (higher) resolution.

·        3x supersampling with MIPMaps at the native game resolution

·        3x supersampling with MIPMaps at the backbuffer (higher) resolution

·        4x supersampling with MIPMaps at the native game resolution

·        4x supersampling with MIPMaps that the backbuffer (higher) resolution

What’s the catch?  Unfortunately, FSAA in Direct3D will not work in all Direct3D games.  Instead, because of the way NVIDIA implemented the FSAA, most of today’s games can’t take advantage of the GeForce 2 GTS’ FSAA. 

Future DirectX 8 games should be able to do just fine, as NVIDIA’s solution will be fully implemented in DX8, but until then, you’ll have to live without FSAA in Direct3D on the GeForce 2 GTS or go after the Voodoo5, which does support it now. 

This is a bit of a disappointment since most racing games, flight simulators, and RPGs are in fact Direct3D games not designed with NVIDIA’s FSAA implementation in mind.  While their FSAA works just fine under OpenGL, the majority of games that are OpenGL-only are first person shooters such as Quake III Arena, which, although they benefit just fine from FSAA, aren’t really worth the performance hit associated with enabling the mode. 

Update (4/26/00): We just received some new information in from NVIDIA regarding their FSAA implementation. The above OpenGL FSAA options are, in fact, the options that will be available on the GeForce 2 GTS, but are not all available using the 5.16 drivers that came with our reference card. Currently, turning on FSAA under OpenGL enables the highest quality 2x screen resolution FSAA, which is what is used in the screenshots on the next page. Driver versions 5.17 and above will offer the other OpenGL FSAA settings mentioned above.

The situation we originally posed for Direct3D is also not 100% correct. While it is true that the current 5.16 drivers do not enable FSAA in every Direct3D game, but it is NVIDIA's intent to have future driver revisions that do enable FSAA for any D3D game. Further, NVIDIA actually has two additional modes for FSAA under D3D, which include:

· 1 x 2 (sampled at 1x in the horizontal direction and 2x in the vertical direction).

· 2x supersampling with a special, more complex filtering algorithm that should produce higher quality images than the other 2x modes mentioned above.