Real-time rendering of underwater caustics

Sammanfattning

Real-time rendering of caustic lighting, such as refractions in ocean rendering, remains a challenging problem in computer graphics. This is due to the computational cost associated with simulating refracted light transport. In modern game engines, caustic effects are therefore commonly approximated using simplified techniques such as projected textures or precomputed solutions. While these approaches are fast in terms of performance, they often lack the ability to dynamically respond to changes in lighting conditions, terrain or water simulation. This thesis explores a cascaded caustic mapping system that utilizes image-space techniques and is intended to be integrated into a modern real-time rendering pipeline for game engines. The proposed method captures water and terrain positions, as well as water surface normals, in order to estimate refracted light positions to generate a caustic pattern in screen space. The work also investigates two separate approaches for incorporating light dispersion, consisting of a ray-based approximation and a post processing method. The implementation is evaluated in terms of performance, memory allocation, and visual quality. The results indicate that the proposed method is capable of producing high quality caustics. While the method is possible to run in real-time applications, the performance requirements is relatively high compared to other operations that typically coexist in a game engine rendering pipeline. This thesis highlights that a real-time caustic simulation system similar to the proposed method may be more feasible than previously assumed, since the method shares several similarities with shadow mapping techniques that may already exist in a game engine rendering pipeline. The post processing approach for light dispersion was observed to provide comparable visual quality while remaining simpler to control and integrate into the rendering pipeline.