caustics are beautiful swirls and patterns that appear when light passes through transmissive surfaces.
demo: https://szj6p7.csb.app
sandbox for the demo above: Caustics - CodeSandbox
a simpler playground: Sandbox Caustics - CodeSandbox
vanilla users go here: GitHub - N8python/caustics
drei docs: GitHub - pmndrs/drei: 🥉 useful helpers for react-three-fiber