Advanced Soft Shadows
Back in the day, one of the major problems developers had when trying to bring realism into a game were shadows. Algorithms were usually far from optimal, and generating accurate soft shadows from area light sources proved to be very difficult subject. Soft shadows are important, as they the provide the needed cues about the environment and objects which become sharper near the casting object and softer further away.
NVIDIA tackled this issue by introducing Percentage-Closer Soft Shadows which is based on a shadow mapping and percentage-closing filtering (PCF) algorithm. Instead of the traditional depth comparison of ordinary shadow mapping, Percentage Closing Soft Shadows returns a value that indicates the amount of shadowing at each point when shading occurs each frame. PCSS also uses the relation that as the PCF kernel increases the shadows become softer to accurately represent the casting of an object. This method proves to be really efficient as it requires no pre-processing, post-processing, or additional geometry.
Advanced Soft Shadows provides a lot of eye candy, specially in realistically textured scenes which require user interaction. This technique also provides a simple way for developers to add high quality and, most importantly, efficient shadows to games. Additionally, it gives the ability to render cascaded shadow maps, and multiple spot lights. Fortunately, it is not taxing as compared to previous shadowing methods which never succeeded for this same reason.