Render occlusion. @parameters
numSamples: Controls the number of occlusion samples per camera hit point. The default is 4.
distribution: Sample distribution can be uniform, cosine, or reflection. The defaul is cosine.
cosineSpread: Sample spread for cosine distribution. The defaul of 1 gives lambertian distribution.
falloff: Falloff values greater than zero create a softer look. Values less than zero give a hard edge. The default is 0.
maxDistance: The max distance at which objects may occlude. The default of 0 is infinite.
useAlbedo: Tint occlusion by material albedo. The default is 0.