How to coat a glass?

[gabrielefx]

Hi guys,

stupid question.

If I apply the roughness to a piece of glass I lost the external surface reflection, the reflection is blurred.

How can I create a glass material with internal roughness but maintaining the surface reflection?

If I mix two specular mats one with roughness and the other one transparent I get a 50% of transparency.

I tried to mix one specular mat + one glossy but I think that the result is not physical.

I think that the mix mat doesn't work like a coating operator. It mixes the two materials like photoshop mixes two layers.

Any answer?

Thank you.

[PolderAnimation]

I don't think 1 shader can do the trick.
In real life you have one glass shader but the structure in the glass is rough and on the outside is polished (smooth).
So you can do 2 things, model the roughness geometrie in the glass (good luck with that) or model (extured) a very thin layer of glass on top of your original and use 2 shaders (one with the rough glass shader and one with sharp reflections).
That is my best guess.

[FooZe]

Would a specular material with heavy scattering and some absorption help here?

Cheers
Chris

[simmsimaging]

Can you map roughness? If so then separate the internal faces of the glass (the inside parts that touch the contents) from the outside ones and only apply roughness there.

If not then it can be done with a fine-grained bump map to create roughness, just map it the same way. This will be more computationally expensive but should work in any render engine.

[Refracty]

you could layout the inner and outer shell on different parts of the UV space and map the roughness, leaving the outer shell 'black'

[Jaberwocky]

Gabrielefx

how about this..

please see attached

Any Good ??

Jaba

[gabrielefx]

thank you for all suggestions.

The best and semi-exact method is to enable the scattering and tweak the scale factor. I noticed that the scattering operator doesn't blur specular highlights on objects that stay on the back of thin glass panels.

For example: create a thin (1cm) glass panel and enable the scattering. Put on the back of this panel two objects with strong reflection, you will see clearly the highlights on these objects seeing through the glass.

The second "fake" method is to mix two materials: 0,9 for a specular mat and 0,1 for a glossy mat with fresnel reflection and glossy=0. In this case we will get two reflections, one blurred and the second one sharped.

[Refracty]

I have tested this but couldn't reproduce the problem.
This is just a box with two specular materials applied.