This is a model of the graph of a degree-3 function of two variables with indented gridlines. The STL file gives a solid model to be used as mold for thermoformed plastic. Because of these, the edges are rounded and the sides are beveled. This model was inspired by the Raising Calculus to the Surface project, and is used as part of the Manipulative Calculus project at Harvard University.

The model was designed entirely in OpenSCAD, but we used Mathematica to find a function with the properties we wanted to for the lessons we will use in multivariable calculus.