For an object made up of a series of short lines, this transformation takes any short line, which has lines before and after it, and converts it to a cubic Bezier with the tangent at the start of the curve equal to the direction of the first line and similarly the end tangent the same as the direction of the third line. The parameter short defines the maximum length of the line which is converted.
The heuristic is due to Maxim Shemanarev http://www.antigrain.com/agg_research/bezier_interpolation.html.
12.1 Smooth Short Lines