*PxrDirt* renders local geometric occlusion. This is useful for applying shading effects to nooks and crevices.

A traditional ambient occlusion effect can be accomplished by setting the occluded color to black and unoccluded color to white. |

### Parameters

#### Occluded and Unoccluded

Resulting colors for occluded and unoccluded shading.

#### Num Samples

Controls the number of occlusion samples per camera hit point. More samples reduces can the noise at the cost of increased render time.

#### Sample Distribution

Possible values are *uniform* and *cosine* (Lambertian).

#### Cosine Spread

Sample spread of rays when using *cosine* distribution. A value of 1.0 gives a perfect Lambertian distribution.

#### Falloff

Falloff values greater than zero create a softer look. Values less than zero give a hard edge when combined with max distance.

#### Max Distance

The max distance at which objects may occlude. Zero is infinite (all objects occlude).

#### Direction

Trace rays in the direction of the surface normal (*outside*), inverse to the normal (*inside*), or in *both* directions.

#### Bias Normal

Add a directional bias to the normal vector. Values must be specified in world space.