This is a very useful script for 3ds max 9 or later. It allows you to create a smooth polygonal surface (with just a few clicks) from three or four connected splines or curves.

With this script you can easily create smooth polygonal surfaces. First you need four shapes. You can draw splines or NURBS curves too.
The shapes must be opened. The direction of the splines doesn't matter, but the endpoints must be in the same coordinate.

Next, on the 'utilities' panel click on the 'Pick 4 splines' button, and now you can select four shapes. The order doesn't matter. In case that you have selected a wrong shape, just click on the 'Pick 4 shapes' button again. After you have picked up all the shapes, the polygonal surface is created automatically with the default settings. Now the 'Polygon Creator' rollout has opened, and you can see some subrollouts in it. Also you can see the 'Accept' and the 'Cancel' button. If you don't want to change anything, click on the 'Accept' button.

Open the 'Segments Settings' rollout. Here you can change the width and the length segments from 2 to 100. Click the '}' checkbutton, to set the segments together. The shape selected first will be the width of the polygon.

Normally the width splines follow the normals of the length splines, and the length splines follow the normals of the width splines. Sometimes it's better to switch off the 'follow normal mode'. You can do this separately with both sides. To understand the 'follow normal mode', see the pictures below. Don't forget: The firstly selected spline will be the width side of the surface!

Open the 'Width Loop Position' or the 'Length Loop Position' rollout. Here you can change the relative position of the edge loops in percent. Values must be between 0 and 100. By default the distance between each edges are equal. The helpers (splines and points) help you to know wich controller directs wich edge. To hide helpers, turn off the 'Show Helpers' checkbox.

The colors help you to understand the usage of this setting. You can change all the colors. The helpers automatically disappear when you close the rollout.

To set the relative position of an edge loop, press the 'set' button. You can separately set the position of the first and the last point of the edge loop. To change values together, turn on the '}' checkbutton. If you want to reset the parameters, press the 'Reset' button.

In the 'Polygon Settings' rollout you can change the color of the polygon, and you can set threshold angle of auto smooth. If you want to flip the normals of the polygon, just click the 'Flip normals' now button.

In the 'Polygon Creator Hide' rollout you can hide the unwanted objects. Turn on the 'Hide Poly.Crea. objects' checkbox to hide the polygons you created. To unhide these objects turn off the checkbox. To hide all other objects (splines), turn on the 'Hide all other objects' checkbox.
Don't forget to press the 'Accept' button, after you have set the parameters.