The Extrude handle is used by the PolyExtrude SOP to control a bevy of
paramaters in an interactive fashion.  There are two copies of most
parameters, the local and global versions.

Parameters:

    group_pivot - Whether to pivot about the group centroid.
    grst_order  - The Rotate, scale, and translate order for the
                  global extrude
    gr[xyz]     - The global rotation to apply to the extrusion.
    gs[xyz]     - The global scale to apply to the extrusion.
    gt[xyz]     - The global translation to apply to the extrusion.
    gxyz_order  - The order to combine the global rotations.
    input       - A group field.  The centroid of this group is used
                  as the default origin.
    onoff       - Whether the handle is visible, 1 means visible.
    px, py, pz  - The local extrude pivot position.
    rx, ry, rz  - The local extrude rotations.
    sx, sy, sz  - The local extrude scales, sz being the inset.
    trs_order   - The local translate/rotate/scale order.
    tx, ty, tz  - The local extrude translations.
    uniform_scale - The uniform scale to apply to the extrude.
    xyz_order   - The order to combine the local rotations in.

See Also: None
