The Source engine is a 3D game engine developed by Valve Corporation. Its unique features include a large degree of modularity and flexibility, an artist-driven, shader-based renderer, accurate lip sync and facial expression technology, and a powerful, efficient and completely network-enabled physics system.
Source code and VMFs for a template "2.5D" Source mod. Side-scrolling and top-down modes supported.
(Formerly the XSI Mod Tool) A completely free version of the Autodesk Softimage modelling package. Plugins for Source, CryEngine 2, Unreal Engine 3, XNA...