Rise of the Tomb Raider is based on a new gamine engine built in-house by Crystal Dynamics called the Foundation Engine. Some of the new features include physically based rendering, HDR, adaptive tone-mapping, global illumination, deferred lighting, volumetric lighting and a brand new in-house hair simulation system. This time, instead of going with AMD for TressFX, or NVIDIA with Hair Works, Crystal Dynamics devised its own hair simulation it is called PureHair. Also in use is NVIDIA's HBAO+, and of course tessellation.
PureHair
Let's talk a little bit about PureHair. In the last Tomb Raider game Crystal Dynamics leveraged AMD's TressFX, which did look great. It moved realistically, and made hair finally look "real" in a game. At its onset it did cost a heavy bit of performance, and initially was slower on NVIDIA GPUs. Later, with driver updates, performance evened out with this affect and with newer GPUs it became a non-issue and the performance drain was a lot lower.
In Rise of the Tomb Raider Crystal Dynamics went down its own path this time and created PureHair. PureHair can add 30,000 strands of hair to a character model, in this case Lara. The individual hairs can react to physics in the game and based on the materials they are moving through like air or water. There are three options, you can turn it off, turn it on, or turn it on "very high" quality setting. With the "on" option this is the recommended setting for most players, and those needing more performance. This is a lower quality version. The "very high" option is the one that can in some cases up-close create 30,000 strands of hair and naturally is the most performance demanding.