Google's Operations Research tools:

Polygon Clipping, Offsetting & Triangulation in C++, C# and Delphi

Robust Tetrahedral Meshing in the Wild.

2D polyline library for offsetting, combining, etc.

TriWild: Robust Triangulation with Curve Constraints

Accurate, detailed, and automatic modelling of laser-scanned trees

Implementation of a robust no-fit polygon generation in a C++ library using an orbiting approach

BlendELF is a 3d game engine for rapid prototyping and game & virtual reality creation.