Nailing down the right look for a water surface can greatly increase the realism of our scenes, especially when dealing with tricky materials, such as the ones that make use of translucency. Getting those nice reflections to show up, the refraction working in the right way, and the animation to feel believable is something we tackled in the previous recipe. On top of that, we can add an extra effect that is often seen in bodies of water: caustics.
This technique, which tries to mimic how the refracted envelope of light rays that the surface of our water body is projecting onto another object works (the bathtub, in our case), is difficult to calculate in real-time renderers. That being the case, we usually rely on approaches that try to fake the effect rather than realistically show it. We'll be exploring one such method in the following pages.