# How to add some blur inside a glass sphere and keep the outside sharp & reflective?

How to add some blur inside a glass sphere and keep the outside sharp & reflective? Blur may not be the right descriptive because there is also some distortion. I'd like to keep it one mesh because I'm going to shatter it and the pieces need the same material.. Here's what I want.

Here's what I have.

Node set up.

Thanks!

• Have you tried increasing the roughness of the Refraction BSDF while keeping it low on the Principled BSDF? – user27640 Feb 8 '18 at 22:36
• @Duane Dibbley - I have but there is some distortion in there that I'm try to achieve as well. – Dontwalk Feb 8 '18 at 22:39
• Perhaps a low density Volume Scatter with anisotropy controlled by a texture, e.g. Noise, Musgrave or Magic. Or using such a texture to control the IOR. Or even combine both ideas. I'm not at my own computer right now, and I can't install Blender to play with it where I am, so I hope you get my ideas without a full answer. – user27640 Feb 8 '18 at 23:05
• Couldnt you give the glass material roughness but add some clear coat for sharp reflections? – 3pointedit Feb 9 '18 at 7:01
• @ Duane Dibbley - This really makes a difference. Thanks! – Dontwalk Feb 9 '18 at 14:25

"Blur" is the right word for describing the effect, but the word for the cause of it is "roughness". Roughness simulates a surface that has microscopic bumps on it. Because of these bumps, light refracts with a little bit of randomness, causing a blur.

All you have to do is increase the roughness to about 0.1, in your case:

Roughness will also blur out the reflections. You said that you want the reflections to be sharp. But look carefully at the reference image. The reflections are slightly blurry, too!

Anyway, here is my result of a sphere with the principled shader and a bit of roughness:

Note that if you would actually need a sharp reflection, you would have to mix a rough refraction with a smooth glossy shader, controlling the proportion by the Fresnel node. (Or you could use the clearcoat feature in the principled shader). This would not be realistic, though, because usually the roughness for the reflection and refraction is the same – unless there are multiple layers in the material, which does not seem to be the case for a simple glass sphere.

• The reason I I thought blur might not be accurate is that if you look at the reference image there is also some distortion. I'll update my question. – Dontwalk Feb 8 '18 at 22:13

It looks to me like your example is a glass sphere with a bubble inside it--perhaps a bubble of air, perhaps a bubble of water or some other material with a different refractive index.

I'm not sure this is the effect you want to recreate, but by mixing two different glass shaders using the fresnel as a mix factor, you can create some cool procedural sphere-within-a-sphere effects:

Parameters to play with to vary the effects include the IORs of the two glass shaders, the colors of the two glass shaders, and the color ramp that controls the fresnel.

Top image: inner glass material has IOR of 3 (as shown in the node setup). Middle image: inner glass material has IOR of 2.