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Is it possible to get the distance a ray travels inside an object with cycles material nodes?

enter image description here

Then map it to a 0-1 range to create a map:

enter image description here

E.g. to adjust the color of a Glass node to make it more transparent where there is less volume between the camera and light:

enter image description here

How can I do this?

The example images above were rendered with the Layer weight node. This only works on spheres.

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It is always the way you ask. Ray length is the distance from previous bounce or refraction.

What might be a bit confusing - you have to apply toning to the inner side (backfacing) of your object, because outside rays return distance from other objects - as ray begins from camera, not from light source.

As far as mapping goes - approaches are different - for instance: http://lesterbanks.com/2012/10/using-blenders-raylength-node-to-create-a-re-usable-custom-absorption-shader/

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  • $\begingroup$ I watched that video a while ago, but I never was able to get satisfying results.. $\endgroup$
    – gandalf3
    Commented Oct 26, 2013 at 23:04
  • $\begingroup$ I have been playing around with this technique and also this one from blender cookie, and I think I have better idea how to use these techniques now. Thanks $\endgroup$
    – gandalf3
    Commented Oct 28, 2013 at 21:49

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