See also Using the Cavity Ambient Occlusion filter.

Strength

Specifies the intensity of ambient occlusion. Negative values can create interesting color effects (such as hot, glowing lava) when you use a color complementary to the Shadow Color.

Sample Radius

Specifies the radius of a sampling area (in screen space). Occlusion artifacts are possible when the radius is set incorrectly in relation to the features on the model. For example, large features can be missed if the radius is set too small, or small features can be missed if the radius is set too large.

Cutoff Radius

Specifies the distance the sampling rays travel from the sampling point into the scene to determine the presence of occluding objects. Decrease this value and the Sample Radius if you do not achieve an acceptable ambient occlusion effect on small objects. In most situations, the Cutoff Radius value should be kept lower than the Sample Radius.

Shadow Color

Specifies the color of the shadows produced by the ambient occlusion effect. Click the color tile to display the Color Chooser window and edit the Shadow Color.

Quality

Good, Better, or Best specifies the number of occlusion samples that occur to improve the appearance of the ambient occlusion effect. The higher the Quality setting, the lower the overall refresh rate in the 3D View.