Is it possible to get the length of a ray inside an object with nodes?

Question

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

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

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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:

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How can I do this?

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

score 3 · Accepted Answer · answered Oct 26 '13 at 22:25

3

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/

answered Oct 26 '13 at 22:25

kivig

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I watched that video a while ago, but I never was able to get satisfying results.. – gandalf3 Oct 26 '13 at 23:04
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 – gandalf3 Oct 28 '13 at 21:49

Is it possible to get the length of a ray inside an object with nodes?

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