Ah, you're most likely talking about Wenzel Jakob's wonderful 2D tool for demonstrating Manifold Walks. Wenzel was actually one of my thesis advisors, and his

Ah, you're most likely talking about Wenzel Jakob's wonderful 2D tool for demonstrating Manifold Walks. Wenzel was actually one of my thesis advisors, and his tool was the inspiration behind this project. :) I was writing an implementation of Manifold Walks out of personal interest and reproduced his 2D tool for debugging purposes. Eventually I realized that caustics in 2D actually look kinda neat, so I spent some time doing research and then fleshed it out into this article + demo.