Caustic Effect Using Cell Noise


The Cell Noise shader is a very versatile shader that is capable of creating a wide range of shading effects. In this simple tutorial, we will cover how to create a caustic effect using a Spot light with the Cell Noise shader connected to a Gobo light filter. Thanks to Slava Sych for the assistance with this tutorial.

Gobo -> Spot Light

  • Start off by creating a plane. We will project the Cell Noise shader through a Gobo using a Spot light.
  • Create a Spot light and point it at the plane. Increase the Exposure of the Spot light.
  • Connect a Gobo light filter to the Spot light.
  • Connect a Cell Noise shader to the Blend attribute of the Gobo.

Cell Noise

  • Change the Cell Noise Pattern to Worley 1.
  • Increase the Cell Noise Scale. In this case, 20 was used in XYZ.
  • Change the Coord Space to UV. This uses the object’s local UV coordinate and in this case looks better for the effect that we want to achieve.

Cell Noise shader using the Worley 1 pattern

Range Shader

We can use the Range shader to linearly remap the output of the Cell Noise shader to create something that looks like a caustic effect.

  • Insert a Range shader in-between the Cell Noise shader and the Gobo.
  • Enable Smoothstep in the Range Shader. 
  • Increase the Input Min attribute and notice its effect on the Cell Noise shader.

Input Min increased to 0.6

  • Reduce the Bias to around 0.01. You should notice that it now looks more like a caustic effect.

Bias reduced to 0.01

  • Go back to the Cell Noise shader and keyframe the Time attribute. You should see something that looks like a caustic pattern!


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