Undulary Surface: A Logarithmic Function‑Generated Surface of Revolution

① This example demonstrates the Undulary surface, a surface of revolution created by rotating a curve derived from a logarithmic function (or its derivative) around an axis. ② The core mathematics involves logarithmic functions, derivatives, solving ordinary differential equations, parametric equations, and the geometry of surfaces and loci. ③ The construction uses GeoGebra commands such as Focus, Derivative, SolveODE, First, Element, Vector, Translate, Angle, Rotate, and Locus, together with a set of auxiliary objects to build the surface step by step. ④ It is intended for high‑school or undergraduate students studying geometry, calculus, or mathematical modeling.