Discrete differential geometry is an active mathematical terrain where differential geometry and discrete geometry meet and interact. It provides discrete equivalents of the geometric notions and methods of differential geometry, such as notions of curvature and integrability for polyhedral surfaces. Current progress in this field is to a large extent stimulated by its relevance for computer graphics and mathematical physics. This collection of essays, which documents the main lectures of the 2004 Oberwolfach Seminar on the topic, as well as a number of additional contributions by key participants, gives a lively, multi-facetted introduction to this emerging field.

Discretization of Surfaces: Special Classes and Parametrizations.- Surfaces from Circles.- Minimal Surfaces from Circle Patterns: Boundary Value Problems, Examples.- Designing Cylinders with Constant Negative Curvature.- On the Integrability of Infinitesimal and Finite Deformations of Polyhedral Surfaces.- Discrete Hashimoto Surfaces and a Doubly Discrete Smoke-Ring Flow.- The Discrete Greens Function.- Curvatures of Discrete Curves and Surfaces.- Curves of Finite Total Curvature.- Convergence and Isotopy Type for Graphs of Finite Total Curvature.- Curvatures of Smooth and Discrete Surfaces.- Geometric Realizations of Combinatorial Surfaces.- Polyhedral Surfaces of High Genus.- Necessary Conditions for Geometric Realizability of Simplicial Complexes.- Enumeration and Random Realization of Triangulated Surfaces.- On Heuristic Methods for Finding Realizations of Surfaces.- Geometry Processing and Modeling with Discrete Differential Geometry.- What Can We Measure?.- Convergence of the Cotangent Formula: An Overview.- Discrete Differential Forms for Computational Modeling.- A Discrete Model of Thin Shells.