<p>Assuming that you are familiar with the concept of BSDFs, the usual way of modelling rough dielectric surfaces (i.e. glass, water, plastics) is to use microfacet-based models like <a href="https://www.cs.cornell.edu/~srm/publications/EGSR07-btdf.html" rel="noreferrer">Microfacet Models for Refraction through Rough Surfaces</a>.</p>

<p>To make it work efficiently in a path tracer you will need a good sampling strategy, like <a href="http://www.eugenedeon.com/project/importance-sampling-microfacet-based-bsdfs-using-the-distribution-of-visible-normals/" rel="noreferrer">Importance Sampling Microfacet-Based BSDFs using the Distribution of Visible Normals</a>.</p>

<p>Also keep in mind, that the mentioned BSDF model tends to get darker as you increase roughness because it neglects the light which gets inter-reflected among micro-facets. This can be compensated, but it's not a trivial thing to do.</p>

CC BY-SA 3.0
2017-07-02T15:25:27.840Z
2017-07-02T15:25:27.840Z
ivokabel
<p>How can a diffused(frosted) glass be modelled in path tracing?</p>

<p>Currently I am able to define a window poly line as a clear glass material where it transmits or reflects the ray. I am not clear though how it should work if the sheet of glass is frosted(diffuse transmission?).</p>

<p><img src="https://i.sstatic.net/gr3jB.gif" alt="enter image description here"></p>

CC BY-SA 3.0
2017-06-30T04:40:05.140Z
If you know how diffuse reflection works (ie not a specular mirror like reflection), what that does with reflected rays, you do with refracted rays.
Alan Wolfe
CC BY-SA 3.0
2017-06-30T04:48:36.567Z
Keep the same parameters, but increase the roughness.
Julien Guertault
CC BY-SA 3.0
2017-07-09T09:22:15.863Z
Thanks for the comments. it shed light on how I got it wrong first.
ali
<raytracing><pathtracing><material>
How can a diffused(frosted) glass be modelled in path tracing
ali
# How can a diffused(frosted) glass be modelled in path tracing

(Asked by: username_0 on 2017-06-29)

How can a diffused(frosted) glass be modelled in path tracing?

Currently I am able to define a window poly line as a clear glass material where it transmits or reflects the ray. I am not clear though how it should work if the sheet of glass is frosted(diffuse transmission?).

![enter image description here](https://i.sstatic.net/gr3jB.gif)

**Tags:** raytracing, pathtracing, material

> **Comments:**
> **username_1**: If you know how diffuse reflection works (ie not a specular mirror like reflection), what that does with reflected rays, you do with refracted rays.  
> **username_2**: Keep the same parameters, but increase the roughness.  
> **username_0**: Thanks for the comments. it shed light on how I got it wrong first.  

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## 1 answers

### Answer by username_3 on 2017-07-02. Score: 7 | Accepted answer

Assuming that you are familiar with the concept of BSDFs, the usual way of modelling rough dielectric surfaces (i.e. glass, water, plastics) is to use microfacet-based models like [Microfacet Models for Refraction through Rough Surfaces](https://www.cs.cornell.edu/~srm/publications/EGSR07-btdf.html).

To make it work efficiently in a path tracer you will need a good sampling strategy, like [Importance Sampling Microfacet-Based BSDFs using the Distribution of Visible Normals](http://www.eugenedeon.com/project/importance-sampling-microfacet-based-bsdfs-using-the-distribution-of-visible-normals/).

Also keep in mind, that the mentioned BSDF model tends to get darker as you increase roughness because it neglects the light which gets inter-reflected among micro-facets. This can be compensated, but it's not a trivial thing to do.


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