A brief history of shadow techniques

Shadows are one of the biggest additions to any rendering framework as they really enhance the perception of depth and volume across a scene. Being a phenomenon linked to lights, they have been studied in graphics literature for decades, but the problem is still far from being solved.

The most used shadow technique right now is shadow mapping, but recently, thanks to hardware-enabled ray tracing, ray traced shadows are becoming popular as a more realistic solution.

There were some games—especially Doom 3—that also used shadow volumes as a solution to make lights cast shadows, but they are not used anymore.

Shadow volumes

Shadow volumes are an old concept, already proposed by Frank Crow in 1977. They are defined as the projection of each vertex of a triangle along the light direction and toward infinity, thus creating a volume.

The shadows are sharp, and they require each triangle and each light to process accordingly...