Command entry:Select an editable patch, editable mesh, editable poly, editable spline, an object that has an Edit Mesh, Edit Poly, Edit
Patch, or Edit Spline modifier applied to it, or an object that has a comparable Select modifier applied to it. 
Modify panel Choose a sub-object level. Soft Selection rollout
The Soft Selection controls allow you to partially select sub-objects in the vicinity of an explicit selection. This causes the explicit selection to behave as if surrounded by a "magnetic field." Partially selected sub-objects within the field are drawn along smoothly as you transform the sub-object selection; the effect diminishes with distance or the “strength” of the partial selection.
This falloff is visible in the viewports as a color gradient surrounding the selection, conforming to the first part of the standard color spectrum: ROYGB (red, orange, yellow, green, blue). Red sub-objects are those you select explicitly. The highest-value soft-selected sub-objects are reddish-orange; they have the same selection value as red sub-objects, and respond the same way to manipulation. Orange sub-objects have a slightly lower selection value, and respond to manipulation a bit less strongly than do red and reddish-orange vertices. Yellow-orange sub-objects have an even lower selection value, and then yellow, green-yellow, and so on. Blue sub-objects are effectively unselected and don't respond to manipulation, except as required by neighboring soft-selected sub-objects.
Normally, you designate a soft selection procedurally, by setting parameters and then selecting sub-objects. You can also “paint” a soft selection explicitly on poly objects. See Paint Soft Selection group.
By default, the soft-selection region is spherical without regard to geometric structure. Alternatively, you can use the Edge Distance option to limit the selection to vertices in contiguous faces.
If a sub-object selection is passed up the modifier stack, and Use Soft Selection is on, the results of modifiers that deform the object, such as Bend and XForm, are affected by the Soft Selection parameter values.
The controls in this dialog let you modify Soft Selection parameters. All sub-object levels share the same Soft Selection parameter values. Soft Selection is available for NURBS, mesh, poly, patch, and spline objects.
Soft selection colors and effect on the surrounding area
Soft Selection Controls in the Caddy
When an editable poly or Edit Poly object is selected, the Select And Manipulate tool is active, and Use Soft Selection is on, the Falloff, Pinch, and Bubble controls are available in a special Manipulate caddy in the active viewport:
At the Vertex and Edge sub-object levels, additional controls appear in the Manipulate caddy; those are covered in the applicable sections of the help.
The caddy controls for Soft Selection are as follows:
For instructions for using the caddy, see The Caddy Interface.
To edit a soft selection in the viewport:
This procedure describes usage of the Customize User Interface Edit Soft Selection Mode feature for editing the Falloff, Pinch, and Bubble values for soft selection.
For more information, including a list of feature sets with which Edit Soft Selection Mode is available, see Edit Soft Selection Mode.
Select an object to edit and activate the feature set from step 1. On the Modify panel, go to the sub-object level you wish to edit, such as Vertex.
The viewport shows your selection in red and the surrounding, soft-selected sub-objects in a color gradient.
The mouse cursor switches to the Falloff symbol.
As you drag, the color gradient changes to show the modified Falloff, as does the Falloff value on the Soft Selection rollout.
The mouse cursor switches to the Pinch symbol.
The mouse cursor switches to the Bubble symbol.
Affects the action of Move, Rotate, and Scale functions at sub-object levels of the editable object or Edit modifier, as well as the action of deformation modifiers applied to the object if they are operating on a sub-object selection (the latter also applies to the Select modifiers). When on, 3ds Max applies a spline curve deformation to the unselected sub-objects surrounding the selection you transform. To take effect, this check box must be on before transforming or modifying the selection.
When on, limits the soft-selection region to the specified number of edges between where you select and the maximum extent of the soft selection. The affected region is measured in terms of "edge-distance" space, along the surface, rather than real space.
This option is useful in cases where you want to select only contiguous sections of geometry. For example, if a bird's wing is folded back against its body, selecting the wing tip with Soft Selection would affect body vertices as well. But if you turn on Edge Distance, set the numeric value to the distance (in edges) along the wing that you wish to affect, and then set Falloff to an appropriate value, selecting and then moving the wing tip would move only the wing geometry.
When on, deselected faces whose normals face in the opposite direction to the average normal of the selected sub-objects are affected by the soft-selection influence. In the case of vertices and edges, this applies to the normals of faces to which they're attached. Turn off Affect Backfacing when you want to manipulate faces of a thin object, such as a thin box, but don't want to affect faces on the other side of the object.
Distance in current units from the center to the edge of a sphere defining the affected region. Use higher falloff settings to achieve more gradual slopes, depending on the scale of your geometry. Default=20.
Expands and contracts the curve along the vertical axis. Sets the relative "fullness" of the region. Limited by Pinch, which sets a fixed starting point for Bubble. A setting of 0 for Pinch and 1.0 for Bubble produces the smoothest bulge. Negative values for Bubble move the bottom of the curve below the surface, creating a "valley" around the base of the region. Default=0.
Displays a color gradient corresponding to the soft selection weights on faces within the soft selection range. Available only when editing patch and poly objects.
If the Vertex Color display property of an editable poly or editable patch object is off, clicking the Shaded Face Toggle button will turn on Soft Selection Color shading. If the object already has an active Vertex Color setting, clicking the Shaded Face Toggle overrides the previous setting and changes it to Soft Selection Color.
In addition to the controls described in the preceding section, you can edit the soft selection in the viewports with interactive controls based on a Customize User Interface action named Edit Soft Selection Mode. This mode is available for the following feature sets:
For each feature set, open the Customize User Interface dialog from the Customize menu, and choose the feature from the Group drop-down list. For many feature sets, but not all, the Edit Soft Selection Mode keyboard shortcut is set to 7 by default. For the rest, such as Editable Poly, you must set the keyboard shortcut with the Customize User Interface controls.
For the basic method of using Edit Soft Selection Mode, follow this procedure.
To enter Edit Soft Selection Mode, press the keyboard shortcut (or click the toolbar button, etc.) assigned in Customize User Interface. When active, drag to use the current mode and click to switch to the next mode. To exit, right-click in the active viewport.
The three Edit Soft Selection Mode modes, along with their mouse-cursor symbols, are:
Paint Soft Selection lets you specify, blur, or revert a soft selection explicitly by dragging the mouse over the selection. This feature is available at sub-object levels with Editable Poly objects, as well as with objects with the Edit Poly or Poly Select modifier applied.
Painting a soft selection does not select sub-objects explicitly; the range of painted selection values goes from orange to blue, rather than red to blue as in standard soft selection. So one possible application is to create a normal selection using standard methods, and then to paint a soft selection around it that would not be possible otherwise. For example, you could select a column of polygons, which normally results in a surrounding vertical oval of soft-selected polygons, and then use painting to widen the soft selection to a horizontal oval (or any other shape).
Opens the Painter Options dialog, with settings for brush-related properties.
Falloff
Pinch
Bubble