This dialog box converts a polyline into a combination of lines, arcs, and splines.
Periodic splines
Select to create a periodic (seamless) spline if the original shape is closed and smooth. If you clear the Cusps and bumps check box, the original shape need not be smooth.
Circular arcs
Select to replace polyline vertices with either line segments or circular arcs. For this option to work, the vertices must be close to a line segment or circular arc.
Cusps and bumps
Select to preserve sharp angles and other features in the original shape.
Error tolerance
Type a tolerance value greater than or equal to zero. The looser the tolerance (that is, the higher the amount of error you will tolerate), the simpler the arc or spline (the fewer points on the resulting arc or spline). Type 0 to create a spline that goes exactly through the polyline's vertices. Type a higher tolerance value to allow the spline to approximate the polyline's vertices.