- Spatial: full-scene 2 or 4 samples anti-aliasing
The most dramatic effect of the T-Buffer engine is its ability to perform real-time full-scene spatial anti-aliasing in hardware. With non-anti-aliased 3D-graphics, when something is rendered, it is rendered to the nearest pixel. When something does not fall exactly onto one of those spaces, the position is approximated to the nearest pixel. When that something is a thin, black, diagonal line on a white background that often falls between two pixels, the computer approximates the location and you get a stair stepping effect known as the "jaggies." If you move that black line around slowly, you will see pixels popping in and out as the approximate location hops closer to one pixel than another. This is called "pixel popping."
What anti-aliasing does is, instead of just approximating the pixel location, it samples the object at a higher resolution than is displayed on screen, then approximates the coloring of the pixels the line partially falls on. So if you have the line falling half on a pixel, that pixel will be a shade of gray. This reduces or gets rid of jaggies and pixel popping because the mind will see the anti-aliased line as smooth and diagonal, unless you look closely.
Above is an example of a scene with and without AA. Note the jaggie phone pole and top of the hill in the top pair of images while these objects look smoother and more realistic in the bottom images.
Another major advantage of anti-aliasing is the reduction of the shimmering effect. This effect is caused when a screen pixel is shared by multiple dots of a texture map. Normally, the computer will choose one dot to render that pixel, which can cause a shimmering effect when the texture moves slightly and contrasting dots from the texture map "take over" the pixel. With anti-aliasing, the pixel is sampled at a higher resolution and then the color of the pixel is approximated from all the dots that share the pixel instead of from just one pixel. This process can also eliminate moiré effects.
The Voodoo5 5500 AGP itself uses two and four-way Jittered Sub-Sample Anti-Aliasing (2WJSAA and 4WJSAA). According to 3dfx, 2WJSAA has the equivalent quality of four-way un-jittered SSAA, and 4WJSAA has the equivalent quality of 16-way un-jittered SSAA.
- Focus: depth-of-field blur
Depth of field is a technique where different parts of an image can be focused upon. It is widely used in film, where the director can force your attention on a specific part of a scene by un-focusing the rest. 3dfx's T-Buffer enables depth of field effects in hardware.
Motion blur is where an object in motion on screen is blurred to trick your mind into thinking it is actually moving. Instead of just having crisp positions for every movement of an object, blurred in-between steps are added to make the movement seem more realistic. Wave your hand quickly in front of you to see the real life equivalent of motion blur.
- Soft shadows and reflections
Unlike in video games, real shadows and reflections rarely have crisp clean cutoffs. Instead, as a shadow or reflection falls from the source object, it fades away. 3dfx has built hardware support for such effects into the Voodoo4 and 5 through the use of the T-Buffer.