Applying Volumetric Sampling Methods to the Rendering of Rain Droplets (2024)

I developed a new technique for rendering physically accurate rain streaks for my master thesis and implemented it in the rendering software PBRT-4.

Inspired by volumetric rendering techniques such as the one implemented in one of my previous projects, I started researching the possibilities of using the same techniques to render rain streaks from a procedurally generated volume. In addition to researching more about existing volumetric rendering techniques, this included research into the physical properties of rain and the challenges these would present. I also implemented a ground truth algorithm to use for comparison with the method I was to develop.

The final implementation and math went smoothly and presented further optimisation possibilities by replacing the smallest rain drops with a uniform fog throughout the scene. The extra predictability presented by volume sampling allows a lot of noise reduction compared to the ground truth method, and allows the algorithm to run on the GPU. The method is still impractically slow for real-time rendering and requires further research to be fully physically accurate, but is currently one of the first approaches to rain rendering in the raytracing scene.

Feel free to contact me if you want to chat! Send me an email at [email protected].