Features of ArsMachina C++ DirectX PC 3D Game Engine:

• Ultra fast, Persistent Heap based storage architecture
• Projected textures soft shadow & light effects
• MMX based dynamic vertex lighting
• Non popping discrete level-of-detail (LOD) system
• Octree/Room based Portal engine for visibility culling
• Flexible & extensible bone based animation system 
• 3D sound rendering with damping
• 3 types of shadow volume shadows (for systems without stencil buffer support) 
• Encaspulated rendersubsystem supporting OpenGL and Direct3D 
• Highly optimized collision tests (cuboid, cylinder, triangle, line, sphere)
• Entity Behavior for easy implementation of complex monster behavior 
• Dedicated Flashlight effect 
• Particle effects
• Shadow map shadows  
• Sphere- & Halolights
• Encapsulated sound subsystem  
• Fabric based surface properties (e.g. sound, friction,...)  
• Slice rendering for depth buffer accuracy increase & non-object based LOD 
• Heuristic path walker & navigator 
• Global object ID scheme 
• D* path planner 
• LGPL CINT C++ interpreter for scripting (compileable for release)
• Log-Streaming concept in each class for efficient error tracking of C++ classes

For a more in depth description of features, go here.