Ok Ive discovered refraction nodes trying to create something like the iOS blur effect - meaning a white blur.

This has worked somewhat with 2d objects, but no matter that the node has the color white when I apply the material to 3d objects the object is too dark -

enter image description here

I don't feel like adding an emissive is correct here. How can I make the blur be white on 3d objects?

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    $\begingroup$ I honestly don't think a refraction shader is what you need. A refraction shader is like glass without the reflective component. For a better explanation, read the Wikipedia article on Refraction. To increase your chances of getting some answers, you may want to include a reference image of what you're trying to achieve; if possible two renditions of the same image, one with and one without the exact blur effect you want to achieve. $\endgroup$ – user27640 Sep 23 '18 at 21:21
  • $\begingroup$ Check the direction of your normals - and please add an inage of your nodes. $\endgroup$ – Rich Sedman Sep 23 '18 at 21:54

It's difficult to be sure without seeing your nodes for the material, but this is most likely due to the way the inner surface is reacting with the roughness of the refraction to refract beyond 90 degrees due to a combination of the angle of incidence of the incoming ray and the roughness. For example :

showing darkness

Depending on your requirement (whether you want the material to actually behave as 'refractive) you could either address this by using the Backfacing geometry input to mix between Refraction and Transparent (effectively hiding the backfaces) :

rough refractive

Or also use the Incoming for for the Normal so that rays are always refracted just for the roughness, not the actual surface angle :


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  • $\begingroup$ With these sort of distances, and looking through at a diffuse reflective material, maybe simply switching off shadows would have quite a big effect, as well? $\endgroup$ – Robin Betts Sep 26 '18 at 12:25

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