Here's the way I understand smoothing in Bryce It's a method called Breaking Angles which tell the program at what degree of an angle light will cast a shadow when striking the loops of polygons which make up an imported object. Smoothing is away to control this breaking angle. When Smoothing is set to 90 degrees. It takes a 90 degree angle in the loop ( or group of loops ) to cast a shadow. If it is set to 45 it takes a 45 degree angle. Breaking angles and welding are two completely different functions. Welding is when polygons and/or loops have identical side by side edges ( the line that connects vertices ) Unwedded the side by side polygon/loop have separate edges. When welded the side by side polygon/loops share one edge When unwedded objects are imported into Bryce the breaking angle of the object is set to 0. Where welded objects are set to 90 degrees.

Stephen Ray