Reducing Caustic Noise in Blender with Cycles

Learn how to reduce noise and fireflies with caustics in Cycles

In this quick tip learn how to use the Light Paths node in Blender’s Cycles render engine to drastically reduce noise and fireflies when rendering with caustics. Normally caustics cause a lot of noise, and thus require a high number of samples to get a clean image. Because of this we commonly disable caustics to speed up the render times and get cleaner images. However, caustics also contribute a lot to the realism of a render as they are responsible for color bleed from bounce lighting.

By using Blender’s Light Path node to mix a glossy and diffuse shader we can drastically reduce the noise, keep caustics enabled, and produce a nicer image.

500 Samples, no caustics, glossy floor

500 Samples, no caustics, glossy floor

500 samples, caustics, glossy floor

500 samples, caustics, glossy floor

500 samples, caustics, glossy mixed with diffuse via Diffuse Ray on the floor

500 samples, caustics, glossy mixed with diffuse via Diffuse Ray on the floor


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26 Responses to “Reducing Caustic Noise in Blender with Cycles”
  1. Posts: 1
    sebas theory says:

    Thank you very much!!!
    i just love Blender after years with maya and cinema4d with blender love at first sight.

  2. Posts: 21
    totsch says:

    Da muss man aber auch erst mal drauf kommen… 😉

    Great information here!
    Thumbs up!

    Btw: Your Blender 2.6 DVD started my addiction! Great work!

  3. Posts: 227

    Brilliant! And like so many brilliant things very simple in hind-sight. This is exactly why I was so resistant to Cycles in the beginning. As soon as I saw all those Nodes I knew stuff like this would take me a decade to ferret out… With Blender 2.5 versions I had come to expect things like this to be coded in or at most checking a box. In fact, I /really/ think this should be a check box option for mats! Thank you mate! This is one of the single best tips I’ve seen for Cycles, so, while on one hand, having to do this plus another 5 or 10 compulsory node fixes with each new material is a /real/ turn off, at least we know how thanks to you guys! Sebastian… you may have just answered my first and biggest question(and gripe! lol)about Cycles. Thank you! Next I want to know how to model accurate GR and QM physics! haha

  4. Posts: 66
    moolah says:

    Awesome tip! Thank you! I think this must be an option in the render settings.

  5. Posts: 3
    Tim says:

    Thank you Sebastian. What an incredibly useful discovery. It helps to think logically through the rendering process.

  6. Posts: 2
    madone says:

    Thank you for the tutorial, though I’ve a question. Do we have to do the trick for all the glossy materials? I try to render a porcelain object made of diffuse and glossy shaders, that is on a plane with a glossy shader too. Everytime I set the nodes, the diffuse seems to take on the glossy and it becomes white. Well I’m lost.

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