Smooth Property Editor

General

Mute	Toggles the deformation on and off without affecting the values of other parameters.
Strength	Controls the amount of smoothing. It represents the number of iterations that each point's position is averaged with its neighbors' positions. Decimal values interpolate between whole iterations.

Feature Preservation

Protects vertices that meet specific criteria from being smoothed.

Boundary vertices	Prevents points on boundary edges from being smoothed. Because boundary edges have neighbors on only one side, they are often pulled strongly in that direction when positions are averaged. This option prevents things like mouths and eyes from becoming distorted by smoothing. It can also help when smoothing assembled surface meshes, because the boundaries of the subsurfaces are not considered connected.
Hard edges/vertices	Prevents points and edges that have been marked as hard (using Modify > Component > Mark Hard Edge/Vertex) from being smoothed.
Crease edges/vertices	Prevents points and edges with crease values set (using Modify > Component > Set Edge/Vertex Crease Value) from being smoothed.
Consider unselected vertices	Controls whether the vertices in the unselected (unsmoothed) area are considered when average positions are calculated when you smooth a selected portion of an object. When this option is on, all of a point's neighbors are considered when the average position is calculated. This allows for a transition at the borders of the smoothed region. You can refine this transition further by creating a falloff. When this option is off, only other selected vertices are considered when calculating average positions. As a result, the selected area is smoothed as if it was disconnected from the rest of the geometry.

Falloff

Allows you to create a gradual transition between the smoothed and unsmoothed areas. Adjust both sliders to achieve the desired falloff profile. If either slider is 0, there is no falloff at all.

The falloff options are unavailable unless at least one of the options above them (Boundary vertices, Hard edges/vertices, Crease edges/vertices, or Consider unselected points) is active.

Radius

Represents how far the falloff area extends into the smoothed region from its borders.

By default, values are in terms of the neighborhood, where 1 represents points that are immediately adjacent to the border of the unsmoothed area, 2 represents points that are one point away from the border, and so on. Values between whole numbers are interpolated.

If you are using a custom filter, values are in terms of the distance type you set.

Sharpness

Controls the shape of the transition in the falloff region. Low values produce an abrupt transition at the beginning of the falloff region (near the unsmoothed areas) and high values produce an abrupt transition near the end of the falloff region. Moderate values produce a smooth transition spread out over the whole falloff region.

Advanced Settings

Reproject	Projects each point back onto the surface of the unsmoothed geometry. As a result, the components become aligned in surface space but the object does not shrink as much. However, the reprojection may miss some spiky details, so the object's shape may still be smoothed down somewhat even when this option is on.
Restrict to curvature type	Restricts the smoothing effect based on the local curvature: Concave or Convex, as determined by the geometric normals (user-defined normals are not considered). For example, you can smooth concavities to eliminate pinching that may occur in elbows and other regions.
Restrict to normal direction	Controls the direction in which points are displaced: None allows points to be displaced in any direction without restriction. Parallel allows points to move only in the direction of their normals (local Y axis). This can be useful, for example, if you want to smooth the height of terrain without affecting the alignment of the map grid or roads. Perpendicular allows points to move only in the direction of their local X and Z axes. This can be useful for aligning components along the surface without smoothing protuberances and indentations. This option is better than Reproject at keeping sharp details, but is less good at aligning components in surface space.
Minimal Displacement	Sets the minimum distance that a point will be moved. If the difference between a point's current position and the average position of its neighbors is less than this amount, the point is not moved. This allows you to smooth noisy areas of an object without affecting areas that are already smooth enough. Values are in Softimage units.
Extrapolation	Exaggerates the displacement of each point. Positive values move the points in the same direction as the smoothing, and negative values move points in the opposite direction. While you can achieve some interesting effects with this parameter, it is particularly valuable as a diagnostic tool: you can temporarily adjust it to see what areas are being most affected by smoothing, and then set it back to 0.

Restrict Direction

Enable	Restricts the smoothing effect to the direction specified by the X, Y, Z sliders. The displacement is calculated according to the other options, and then projected onto the specified direction.
X, Y, Z	Vector specifying the direction in which to restrict the smoothing effect. The values are automatically normalized so the displacement is not scaled; use Extrapolation if you want to scale the displacement.

Custom Filter

Use custom filter

Activates the custom filter options, allowing you to specify a different algorithm than the default smoothing using the other options on this tab. All the other options on the General and Advanced Settings tabs also work in conjunction with custom filters.

Settings

Distance type

Determines the criterion used to measure the distance between points:

Neighborhood uses connectivity as a measure of distance. This is the same distance type used by the default smoothing algorithm, but the custom settings give you greater control over the distance and profile.

The Distance between two points is the least number of edges in any path between them. Thus, adjacent points have a distance of 1, points that are separated by two edges have a distance of 2, and so on. Even though points are always separated by a whole number of edges, you can still use decimal values for the distance; values between whole numbers are interpolated, so a distance of 1.5 yields a displacement halfway between the displacements achieved by distances of 1 and 2.

A characteristic of this distance type is that edge lengths tend to become equal at high Strength values.

Edge Path Length uses the sum of the edge lengths in the shortest path between two points as the measure of distance. Distance values are in Softimage units.

A useful characteristic of this distance type is that the ratio of edge lengths is maintained, even at high Strength values.

Use Max neighborhood depth to prevent excessive calculations.

Spatial (consider neighborhood) uses the distance between points in 3D space, as long as the points are connected by edge paths. Distance values are in Softimage units.

Use Max neighborhood depth to prevent excessive calculations.

Spatial (ignore neighborhood) uses the distance between points in 3D space, whether or not the points are connected. The Distance values are in Softimage units.

This is the only distance type that can be used with particles, since the points in a point cloud are not connected. This distance type is also useful for hair because only points on the same guide hair are connected.

Use Max visited vertices to prevent excessive calculations.

Distance

The maximum distance between two points for them to be considered "nearby". Units depend on the Distance type.

Smooth profile

Controls how the positions of nearby points are weighted as a function of distance. The horizontal axis represents the distance of a nearby point, where 100 is the maximum distance set by the Distance slider. The vertical axis represents how strongly points at the corresponding distance are weighted when calculating the average position. Positive values pull a point towards its neighbors, and negative values repel it.

You can select the profile curve and edit it using the mouse and the same keyboard commands as the animation editor, or right-click to display a menu.

Computation limit

Prevents excessive calculations caused by evaluating too many "nearby" points. Setting values too high may result in long computation times when Distance is high, and setting values too low may prevent the Smooth operator from evaluating all nearby points.

Max neighborhood depth	This option is used when Distance type is Edge Path Length or Spatial (consider neighborhood).
Max visited vertices	This option is used when Distance type is Spatial (ignore neighborhood).