Radius - this parameters determines the amount of area (in scene units) where the VRayDirt effect is produced.

Texture Map - this texture map control the radius area. The texture intensity is multiplied by the radius to calculate the final radius at a given surface point. If the texture is white at a given surface point, the full radius value is used. If the texture is black, a radius of 0.0 is used.

Occluded color - this is the color that will be returned by the texture for occluded areas. You can use a texture map or Cinema4D shader for this parameter.

Unoccluded color - this is the color that will be returned by the texture for unoccluded areas. You can use a texture map or Cinema4D shader for this parameter.

Distribution - this parameter will force the rays to gather closer to the surface normal. The effect is that the dirt area is being narrowed closer to the contact edges. For ambient occlusion, set this parameter to 1.0 to get distribution similar to the ambient lighting on a diffuse surface.

Falloff - this parameter controls the speed of the transition between occluded and unoccluded areas.

Subdivision - controls the number of samples that takes to calculate the dirt effect. Lower values render faster but produce a more noisy result.

Bias (X,Y,Z) - these parameters will bias the normals to the X (Y,Z) axes, so that the dirt effect is forced to those directions. Consider that these parameter can also take negative values for inversing the direction of the effect.

Ignore for GI - this check-box determines whether the dirt effect will be taken into consideration for GI calculations or not.

Consider same object only - when on, the dirt will affect only the objects themselves, without including contact surfaces and edges. If off, the entire scene geometry is participating for the final result.

Invert normal - this option allows to revert the effect with respect to surface normals - e.g. instead of crevices, open corners will be shaded with the occluded color.

Work with transparency - when on, VRayDirt will take into account the opacity of the occluding objects. This can be used, for example, if you want to calculate ambient occlusion from opacity-mapped trees etc. When off (the default), occluding objects are always assumed to be opaque. Note that working with correct opacity is slower, since in that case VRayDirt must examine and evaluate the material on the occluding objects..

Ignore Self Occlusion - allow dirt to be self occluded.