Refractive Caustics Using the Sky Shader


I discovered recently (purely by accident), that you can get some pretty convincing refractive caustics using just the Sky shader.

Previously, I was under the impression that they could only be achieved using an emissive shader. However, using a HDR map with some high dynamic areas like a window or sun can give you some impressive results.

Tutorials here: MtoA, C4DtoA.