Shadow Proxy Documentation
Since we need to save as many draw calls as possible, we will create shadow proxy for most of the objects we have in the game. It helps due to the fact, that shadowmap rendering doesn't care about any surface property of a material, only geometry, so we can actually merge what would be many drawcalls into one. Shadow proxy is an optimized geometry of the model without alphablended parts (decals mostly) with a dedicated single material ID and a shadow proxy sub set in CryENGINE material.
For more information please take a look at the CryENGINE documentation.