NVIDIA Plug-and-Play Tessellation is an advancement of what used to be GeometryWorks. The Tessellation libraries and tools that NVIDIA has put together allows for developers to greatly enhance the amount of details the players see. With these libraries it is relatively easy to add tessellation to the AnvilNext game engine, allowing to quickly generate tessellation displacement maps suitable for tessellation from pre-existing objects in the library. The library also intercepts DirectX draw calls, analyzes the vertex shader currently being used, and adds its own tessellation shaders, so developers can simply add to the displacement map generated by the Displacement Map Tool.
Tessellation allows what would normally be a single, flat texture that does not alter the lighting, or shadowing of the game to become a single “three dimensional” structure inside the game to which HBAO+ can shadow correctly and affect how PCSS casts over the area. The addition of geometrical detail plays a key role in this, and is what NVIDIA has been working on for quite a while.
In Assassins Creed Unity, Tessellation has not yet been released as of the moment of writing this article, however NVIDIA has confirmed that it will bring GeometryWorks DirectX11 with a later update.