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.

The tutorial scene file can be downloaded here. The shark model used in this tutorial can be downloaded here.


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!



Scene settings

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