To accurately render skin, additional techniques and technologies are required. In games and the real world, light bounces from most objects and surfaces, which we can accurately and easily render with any number of technologies. In comparison, light striking skin is absorbed and diffused, with some rays being emitted, though at a lower intensity. Without a suitable technology simulating this effect, character skin is uniformly lit, detracting from the quality of the picture.

In Killing Floor 2, players are surrounded by friends and enemies at all time, making accurate skin rendering a must. The solution for Tripwire Interactive: Jorge Jiminez's Screen Space Sub-Surface Scattering (SSSSS), an improved version of Sub-Surface Scattering (SSS) seen in several recent games.

Compared to traditional SSS, SSSSS only shades skin visible from the player’s perspective, which is particularly important for Killing Floor 2, where hundreds of enemies can attack simultaneously. Without this SSS addition, the performance cost would be crippling. SSSSS also introduces level of detail features, ensuring Subsurface Scattering on a distant enemy is rendered at a lower quality with a correspondingly low performance impact. Again, key for a game with hundreds of characters visible across a level.

The interactive comparison below highlights the benefits of Subsurface Scattering on two of Killing Floor 2’s ‘zeds’ in a room with high-intensity lighting.