Hard Shadow Anti-Aliasing for Spot Lights in a Game Engine

Real-time shadow rendering is desirable in several computer graphics applications, such as games. The most popular game engines typically provide support to this feature through the traditional shadow mapping algorithm. Unfortunately, shadow mapping is well known to generate aliasing artifacts along the shadow boundary, decreasing the realism of the rendered virtual scenes. In this paper, we aim to minimize these artifacts by implementing an anti-aliasing hard shadow technique in a game engine. Even with the limited source code access provided by some game engines, we demonstrate how to implement an improvement of the shadow mapping technique for shadow anti-aliasing. We validate our approach by implementing the revectorization-based shadow mapping technique for spot lights in a commercial and popular game engine, the Unity 3D. We show that, in this case, we are able to improve the shadow visual quality at the cost of only ~1.2% of loss, in average, in the frame rate. Finally, the results indicate that the proposed implementation is ready to be integrated into Unity projects which use spot lights as a source of direct illumination.