Screen Space Ambient Occlusion

This is a screenshot of the SSAO parameters:

radius: This sets the radius/area that the samples are taken from around each pixel.
samples: The amount of samples at each pixel.
capSamples: This is an error threshold used in the sampling process. It sets the amount of maximum tries to find a unique sample.
threshold: Threshold is the "distance" in depth that the occlusion looks in.
falloff: Defines the falloff/slope for the algorithm that calculated each sample's addition to the occlusion sum.
cutoffAngle: This parameter sets the threshold/cut off angle for avoiding self occlusion of the surfaces. If this is to low flatter surfaces start to get gray and dirty with self occlusion.
gain: Simple multiplier to get the occlusion result in a good range to use.
calcNormals: Toggle to set whether to you want to calculate normals internally or if you want to feed it with a pre rendered normals pass.
normalsFov: FOV angle used in the normals calculation.
postBlur: Enables or disables the angle aware guassian post blur filter to smooth the SSAO sampling.
xPixels & yPixels: Amount of guassian blur in X and Y directions.
blurAngle: Angle threshold for the "smart" guassian blur. This value determines what surrounding samples to be used in the blur process due to the angle differens of the normals. If the surface have a greater difference in direction than this parameter the sample is not used in the blur. This results in a smooth blur that doesn't destroy object boundaries or sharp features.