One major new feature NVIDIA claims is the Per-Pixel Shader. They say the it is capable of doing seven pixel operations in a single pass. These operations are:

1. Base texture
2. Per-pixel bump mapping
3. Per pixel diffuse lighting
4. Per-pixel specular lighting
5. Colored fog
6. Ambient light
7. Alpha transperency

So what does this mean?

A quick look at the list gives us four per-pixel operations that are not particularly interesting or special. Drawing a base texture is one of those normal everyday operations that all current consumer 3D accelerators can do in one pass. Colored fog is another one of those one-pass jobs, at least for the GeForce 256. Ambient light is directionless light, which basically means it's easy addition, so any card that cannot do ambient light in one pass had better go to school on the short bus. And lastly there is the alpha transparency, which is yet another one of those things that could always be done in one-pass on a GeForce 256.

So we are left with three operations to puzzle out in this "seven operations in one pass, per-pixel shader" orgy. Per-pixel bump mapping, per-pixel diffuse lighting and per-pixel specular lighting; what are they and how do they come in? Let us illuminate the issue.

There are three main types of polygon lighting techniques currently used in games, lightmaps, flat shading and vertex lighting. NVIDIA has added a fourth type of lighting option, per-pixel lighting, which should be a more accurate and attractive method of lighting. Here is a run down of the four types of lighting.