Cavity allows the detection for concavity or convexity on your landscape and use that to apply the selected layer according to the main setting of rules defined

TerraPainter scan the terrain locally for each point and calculate the average height that is used to determine if the

You can tweak the detection using 3 parameters

Radius is how large is the neighborhood to scan for each point.

Scan Resolution is the the scanner resolution used to compute the average height

Strength is a kind of weight that is how strong is the contribution to the final layer weight