How to create Caustics in Blender

A while ago, The topic Caustics was really hyped in the Blender Community because it was supposed to be a feature within the upcoming Version of Blender 3.1. But unfortunately this isn't the case. It is currently only a feature in some unstable, unusable third party builds of Blender.😢 But crying isn't an alternative, so I show you how to create Awesome Caustics in Blender with the help of the LuxCoreRender Engine.

Latest update February 21, 2022

Installing Lux Core Render

The Lux Core render Engine is currently only available for Blender 2.93 or 2.93 LTS. Any newer Version will crash. I would recommend getting the portable Version, because that allows you, to install the ACES color space which I also used in the Demo file I provide.

Her you can download the LuxCoreRender Render Engine.

You will get a .zip file, which you can install like every other Blender Add-on under Edit > Preferences… > Add-ons > Install…. And then just search for the file.

If you did everything right you should be able to besides Eevee and Cycles now also select the LuxCoreRender Render Engine.🥳

Working with Lux Core Render

Like Cycles, LuxCoreRender is a separate Render Engine.
The Problem with that is, a separate system for Materials which works a bit different.
But since LuxCoreRender render is primarily being used inside of Blender, LuxCoreRender knows, how to work with Cycles Materials and can translate then most cases. By clicking on Use Cycles Settings.

But in general it should be easy for advanced Blender user, to find out, how LuxCoreRender works since it is relatively simple to Cycles.

Halt Conditions

One odd thing about LuxCoreRender Render Engine is, that by default, the rendering process won’t stop.
To fix this. You have to set Halt Conditions. You can choose between samples, time and even a Noise threshold.

(These are all the options that are also available in Cycles since Blender version 3.0 which the Blender developers got inspired from the LuxCoreRender with the difference, that the Noise Threshold works in LuxCoreRender.)

Denoise

The other thing, that is a bit weird in LuxCoreRender is the Denoising, just like in Cycles you can check the box but if you render you won’t get the denoised image.
To change  that, you have to get into the Compositor and connect the Denoise Output of the Render Result Node with the Output Node.

Activating Caustics

In LuxCoreRender there is this magic box to check called Light Tracing which you can find under Light Paths. If you activate this box, you will get Caustics.

To try this out, you can use the Demo file I provide, which you can download here.
Keep in mind, that I am also using the ACES color space for all my projects. Here you can find out, how to use it.

Provoke Caustics

To get Caustics, you need a Transmissive Material like Glass and a Light Source in your Scene.
But the way to get more visible and more defined Caustics is by having a strong small light in your Scene and having a dark background to increase the contrast.

Here you can see the difference between a Point Light with the size of 0.5 meters and 0.001 meters.

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