Voodoo5 - FSAA information

FSAA Overview

Jarrod in tech support

FSAA is an acronym for Full Scene Spatial Anti-Aliasing. It is the primary feature of our T-Buffer technology. The other features of the T-Buffer include Soft Shadows, Motion Blur, Depth of Field, and Reflectance Blur. These other effects must have software support to be implemented. FSAA, however, is API (Application Programming Interface) independent and works on virtually every game.

Our T-Buffer technology is proprietary. It is considered to be a modified Accumulation Buffer (or A-Buffer), which has been part of SGI (Silicon Graphics, the inventor of the OpenGL or Open Graphics Library) rigs for many years. Until now, FSAA has been extremely difficult to implement successfully in real-time on consumer level video boards because of technological restraints, i.e. bandwidth limitations and lack of processor power. Our T-Buffer is revolutionary in this respect. For the first time hardware rendered, API independent FSAA is available on consumer level boards at a reasonable price.

There are two modes: 2X and 4X FSAA. The specific method of our FSAA implementation is referred to as RGSS, or Rotated Grid Anti-Aliasing (a form of JGAA, or Jittered Grid Anti-Aliasing ).

Memory requirements:

Depending upon the game you will be able to use either 2X or 4X FSAA at a certain resolution and color depth. Because of the extreme requirements in memory for FSAA to function, it is recommended that you use FSAA at resolutions of 800x600 or 1024x768 to start with, and then work your way up from there to see if the game is playable with such a setting.

Why such constraints?

FSAA requires a great deal of memory and fill-rate. 2X FSAA takes 2 sub-samples of each pixel rendered. 4X FSAA takes 4 sub-samples of each pixel rendered. So it's obvious to see just by the numbers that FSAA takes more pixels than would otherwise be used to render the image. The reason for this extra sampling is very simple. You need more source data to render the image in a more life-like and realistic manner. The cost with today's technology is that you can't run most newer games at very high resolutions with all features enabled (such as 32-bit color, mip-map dithering, triple buffering, and FSAA).

One of the most polygon intensive games on the market currently is Quake3 Arena. The power of the Voodoo5 5500 becomes evident here. You can run Quake3 at an 800x600 resolution (in 16-bit color) with 4X FSAA turned on, and the gameplay is smooth. The image on the other hand is almost indescribable. Most people who have seen 4X FSAA turned on for the first time are hard pressed not to let their jaw drop. Others find that they want to use the 2X FSAA and go up to 1024x678 or just turn off FSAA altogether for even higher resolutions.

Other games which do not push such an extremely high number of polygons can be rendered at higher resolutions (1024x768 and above) with 4X FSAA and are completely playable. Starsiege Tribes is one of the more popular games in this respect, and looks completely awesome at a setting of 1024x768 with 4X FSAA turned on, and is completely playable. Another excellent example is Ground Control.

Why the lower frame rates with FSAA? Isn't 3dfx all about FPS (Frames Per Second) speed? What about my benchmarks?

Yes, traditionally our motto is to try and render a 3D scene at 60 FPS, that's the goal. On a lower-end CPU, with FSAA enabled, the frame rate will tend to drop below 60 FPS. Many will try and use this as an automatic disqualifier for FSAA and its enhancement of the game. Our stance here at 3dfx is simple, play your games with our FSAA turned on (preferably the 4X mode, but 2X is nice too) and you will never, ever go back to non-FSAA games again (not unless you're forced to anyway). Try it and see. One day with the 5500 at 4X mode is long enough, turn off FSAA or put in another video card and you'll immediately see how used to it you've become. FSAA spoils you. :O)

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