Create two polygon primitives of your choice with low poly count.

Select them, make a polygonal boolean operation (Polygons - Booleans - Union, you can change the operation type afterwards).

Select the resulting polySurface and smooth it (Edit Polygons - Smooth),
edit polySmoothFacet divisions Attribut as required.

Now, when you move one of the boolean members, the resulting polySurface is updated in its smoothed state, but notice that sometimes hard edges appear on your model. This is because smooth works on a per face basis (refere to the Manual: Polygonal Modeling p. 229 ff "Emulating subdivision surface workflows"), so modify the .inputComponents of the makeGroup node (usually makeGroup1) upstream of the polySmoothFacet node.

Select the resulting polySurface, open Hypergraph, click Up and Downstream Connections, navigate to the polySmoothFacet node, check the name of the makeGroup node.

Type following command in the command line (? of makeGroup? is your index):

setAttr makeGroup?.inputComponents -type "componentList" 1 "f[*]" ;

All Faces of the polySurface are smoothed, now.


Three more Tips:

After you have booled the original poly primitives, you can use the resulting polySurface(s) for further boolean operation(s), and smooth the desired, final polySurface.

Try to create a subdivSurface from the resulting (unsmoothed) polySurface, but you should have a really low poly count. This will be interesting in MAYA 3.0, where subdivision surfaces are part of the render tree and need not to be tesslated any more.

My best results I have achieved with polyCubes, subdivisions in X, Y, Z of one, and a high polySmooth.division value. So, generally, the lower the original poly count, the higher the polySmooth.division value, the cleaner the resulting poly mesh.

And now a special bonus Tip,

How to emulate Cinema 4Ds Metasplines (really nice feature) with an extruded polySurface.

Create a curve (degree 1 linear, extrude path) and nurbsCircle (profile).
Note: you can also use a nurbSquare, I prefere the circle because of its history node.
Now we need the extrude options with Surfaces - Extrude OB, change following options:

Style: Tube
Result Position: At Path
Pivot: Component
Orientation: Profile Normal
Output Geometry: Polygon
Type: Quads
Tesslation Method: General
U,V Type: Per Span # of Iso Parms
Number U,V: 1
Extrude.

Edit makeNurbCircle node: Degree Linear, Sections about 4.
Close the ends. Right-Click the polyTube, choose edge from the marking menu.
Now use Polygons - Append To Polygon Tool (try Fill Hole with a selected edge, my did not work as it should) and click on the desired edges to form closing faces.
Vertices on top of each other have been created during the modeling process, that prevent continuity in the smoothed object afterwards.
Rightclick the tube, choose vertex from marking menu. Select all the vertices, goto Edit Polygons - Merge Vertex OB, set the distance to about 0.2, MergeVertex.
There you are, the spline boole member is finished (test its history by moving the CVs of your path curve).

Have much fun with your Metaobjects. Never stop thinking, the Koernel !!!