With the GeForce 185 drivers, NVIDIA has introduced a new graphics option: ambient occlusion. This allows the generation of shadows caused by indirect light in 3D scenes which will get you a noticeable quality improvement just by enabling an option in the driver control panel.
What is ambient occlusion? In a 3D scene, the lighting of each element is made up of several components. The first are the best known and the most obvious as they are what we think of first: direct sources of light. The second are often forgotten but are also very important. In reality, every object also reflects part of the light it receives. Otherwise put, each object in the scene becomes a source of indirect light for every other object and this participates in overall lighting.
If you want to render this overall result you need to represent all these sources of indirect light with a global illumination algorithm but this is very demanding and costly in terms of performance. In real time 3D, these sources of indirect light are in general represented very simply by a constant, ambient light. This consists of a sort of base lighting to which are added other light sources. Although this approximation means avoidance of excessively dark scenes, it is also a gross simplification of reality and this undermines the realism of a scene.
The solution which compensates for this fault without having recourse to global illumination is known as ambient occlusion and consists in calculating how much ambient light arrives at each point, or rather does not arrive. As the name of the technique indicates, it determines what occlusion of indirect light there is for each point and, from that, reduces the value of ambient light that is applied to it. Generally speaking then, it renders on the whole scene any soft shadows created by obstacles to indirect light, which adds depth to the scene.
To the left, a standard scene, to the right a scene with ambient occlusion.