The Smooth command averages the positions of curve and surface control points and mesh vertices in a specified region.

The Smooth command evens out the spacing of selected control points in small increments. This command is useful for removing unwanted detail, and for removing loops in curves and surfaces.

Note: On mesh objects use the Weld command before smoothing in order to prevent the mesh from pulling apart.


4 Select curves, meshes, or surfaces to smooth and press Enter.

The selected entities will appear to melt, losing detail due to the averaging of the positions of the control points.

To smooth part of a curve or surface

1. Select a curve, surface, or mesh to smooth.
2. To smooth a region, turn on control points, and select the control points in the region of the object to smooth.
3. Start the Smooth command.
4. Click the check boxes for the coordinate directions and adjust the Smooth factor.

The selected control points will move slightly, smoothing the curve or surface.

Note: To set one check and clear the others, right-click the check box.

Smooth Options

Smooth X / Y / Z

Smooths only in the specified x-, y-, or z-direction.

Fix Boundaries

Prevents edges and endpoints from being included.

Meshes: Vertices along naked edges will not be modified.

Curves: End control points will not be modified.

Surfaces: The control points along the boundaries of the surface will not be modified. The edges and trims of trimmed surfaces will be modified if they do not coincide with the surface boundary.


If all of the object control points are selected, Rhino perceives this as the whole object being selected.
Fix Boundaries may cause undesirable seams or singularities in closed curves and surfaces.

World / CPlane / Object coordinates

Use world, construction plane, or object coordinates to determine the direction of the smoothing.

Note: Smoothing in general is done by moving control points towards the average of the neighboring points. In Object coordinates mode, each control point uses an XYZ frame that is identical to the object-aligned gumball frame for the point. This means Z is the curve/surface/mesh normal, and X and Y are directions derived from the UV directions or the curve direction.

Smooth factor per step

Sets an amount of smoothing.

0 to 1

The curve control point toward the average.

Greater than 1

The curve control point moves past the average.


The curve control point moves away from the average (roughing).

Number of smooth steps

Specifies the number of steps to iterate the smoothing factor through.


Many steps and small factor are preferable to setting the factor above 1.
Setting the factor to 1 means the original control point locations are ignored, the new locations then are the average of the neighboring points.

See also

Edit curves

Edit surfaces