Openscad function plot

This is a function plot utility for OpenSCAD enviroment. Designed as a module, it renders the graph of an external user-defined function. The function domain may be either a triangle or a quadrilateral. The ploting grid is triangular. The stl files is an example, it is not meant for printing.

UPDATED 01-23-2016: A new version correcting a flaw that produced degenerated polygons in some instances. The examples and comments also have minor changes.