On some objects in the game, for example the foundations of both the Stone Bridge and the church (on the Medium French Village map), we make use of a shader technology called displacement mapping.
Displacement mapping is a technique for adding geometric detail to the mesh the shader is applied to.
Compared to with normal maps, which works by just altering the surface normal to fake the amount of detail in the mesh detail, displacement mapping alters the mesh itself.
I’ve made some examples that i hope can show you how displacement mapping works and looks with a normal map and a diffuse map.
For this example I’ve used the texture maps from the Stone Bridge in “Medium french Village” more precisely from the foundation of the bridge.
These are the images we use, they have all been drawn in Photoshop, but could just as well have been renderdt from a high-poly object. Rendering maps from high-poly objects gives the best and most accurate result, but it takes more time to model a high-poly object to render from, than it does to draw grey-scale normal or displacement map in Photoshop, but if time is on your side highpoly objects is preferred, if time is not so much on your side drawing them in Photoshop will do fine ;)
This is the map that defines the surface main color look.
This is used to faking the lightning of bumps, dents, scratces and so on without added more polygons.
This is the map we use to for the displacement mapping, where black represents the absolute lowest and white represents the highest point. It adds a lot of details to the conture of the object.
If you want to know more about tesselation, Nvidia has published an article about it here: http://www.nvidia.com/object/tessellation.html
Over and out!