CadLib is A .NET DXF file manipulation library with 2D and 3D support that also handles export to image formats and PDF.

KernelCAD is an embedded CAD software, which adds interactive 3D solid modeling functionality to any Windows application.

Graphics libraries for Delphi developers, such as an OpenGL canvas, hidden lines algorithms, and geometry data management.

Object oriented 2D/3D graphics libraries with AutoCAD file format support, as well as a web-based version.

Offers components for CAD/CAM software, such as the 3D Core CAD-engine, the SmartFit 3D best-fitting application, and related functionality.

Cadmai ist a parametric and relational CAD module that can be integrated as a intelligent viewer in other applications.

DWGDOMlib and DXFDOMlib modules for reading and manipulating DWG and DXF files from within .NET applications.

An educational project trying to develop a gesture-based interface for 3D modeling. It uses wxWindows, ACIS, OpenGL and DevIL.

Offers technology to display and manipulate 3D CAD and terrain models, designed to be embedded into GIS, CAD, technical documentation and e-learning applications.

A library for 2-D and 3-D geometric calculation in C, with functions for shape generation, geometric evaluation, intersection, and offsetting and filleting.