The gradational filter redefines the null nodes outside a clipped region by computing the distance to the closest defined node and multiplying the g-value for the closest defined node be a scalar based on the distance to that node.  For example, if the closest distance from a null node to a non-null node is very small, the null node will be reassigned a value that is very close to the closest defined node.  Conversely, as the distance increases, the reassigned value will decrease.

Pre-Filtering:  If desired, node values below a specified threshold can be set to null before the gradational filtering takes place.

Surface Limiter:  When gradationally smoothing models that have been clipped by an upper surface, the same surface must be used to constrain the smoothing.  Otherwise, the gradations will be projected above the truncation surface (center diagram shown below).

Distance:  This setting defines the lateral width of the gradation.