From BlenderWiki

Cast Modifier

Mode: Any mode

Panel: Modifiers (Editing context, F9)

Description

This modifier shifts the shape of a mesh, curve, surface or lattice to any of a few pre-defined shapes (sphere, cylinder, cuboid).

It is equivalent to the To Sphere button in the Editing context → Mesh Tools panel and the To Sphere command in the Mesh → Transform menu of the 3D views in Edit mode (⇧ ShiftCtrlS), as well as what other programs call “Spherify” or “Spherize”, but, as written above, it is not limited to casting to a sphere.

Hint: the Smooth modifier is a good companion to Cast, since the casted shape sometimes needs smoothing to look nicer or even to fix shading artifacts.

Important

For performance, this modifier works only with local coordinates. If the modified object looks wrong, you may need to apply the object’s rotation (CtrlA), specially when casting to a cylinder.

Options

Cast modifier.

Type: Menu to choose cast type (target shape): Sphere, Cylinder or Cuboid.

X, Y, Z: Toggle buttons to enable/disable the modifier in the X, Y, Z axes directions (X and Y only for Cylinder cast type).

Factor: The factor to control blending between original and casted vertex positions. It’s a linear interpolation: 0.0 gives original coordinates (aka modifier has no effect), 1.0 casts to the target shape. Values below or above [0.0, 1.0] deform the mesh, sometimes in interesting ways.

Radius: If nonzero, this radius defines a sphere of influence. Vertices outside it are not affected by the modifier.

Size: Alternative size for the projected shape. If zero, it is defined by the initial shape and the control object, if any.

From radius: If activated, calculate Size from Radius, for smoother results.

VGroup: A vertex group name, to restrict the effect to the vertices in it only. This allows for selective, realtime casting, by painting vertex weights.

Ob: The name of an object to control the effect. The location of this object’s center defines the center of the projection. Also, its size and rotation transform the projected vertices. Hint: animating (keyframing) this control object also animates the modified object.