# Glass: Increase “Transmission Roughness” as the object behind goes far

In the real world, there are some rough glasses that as objects behind them go away, they (the objects) become more blurry, but when we stick an object just behind this type of glass, it's almost shown clear (also some materials has this property in their reflections, that's another question).

For clarification, I photographed these examples:

1. When the object (my hand) is stuck behind the glass:

1. When the object goes a little far from the glass:

2. Bringing it farther:

How do you achieve this effect in Blender with Cycles engine? (mine is Blender v2.82)

• If you add a similar displacement map for the glass it will work fine. Just don't forget to change the color space to Non-Color on the texture's node. textures.com/browse/overlays/114557 – FFeller Feb 27 at 6:56
• With a noise texture displacement, will it work like what I've explained? (the more distance from the glass (depth) the more roughness for that object (or that point))? – H. Farid Feb 27 at 7:29

Cycles is physically based so you don't need to add anything to a regular transmissive shader. Add a Principled BSDF to you plane. Set the transmission to 1. You can tweak the IOR but the default value of 1.45 is fine for the purpose.

The setup:

Result :

• Hey, we posted our answers with a difference of fewer than 60 secs! So which one should I mark as the best??!! – H. Farid Feb 27 at 10:03
• Your call ! Yours goes a bit further and tries to mimic the noisy patterns along the glass, but if you do I would recommend to change a bit your question to also include that part, since in my opinon, this was not part of the question itself. Anyway no big deal as long as you mark it as solved – Gorgious Feb 27 at 10:15
• So my question was about rough glasses, and the noisy bump has almost the same result as increasing the roughness (in my example the roughness is set to zero but the noisy bump makes it rough). – H. Farid Feb 27 at 10:18

I achieved that by using a noise texture to create a bump map and assigning it to the Normal property of the Principled BSDF Shader (while the Roughness is set to zero). Here is the result:

And the nodes:

• Never realized you can use a Bump map to simulate glass roughness :). You can also play with the Transmission roughness slider to adjust light scattering inside the glass. – Jachym Michal Feb 27 at 17:02