Plexiglass glowing side faces

[alexandroskapsalis]

I am trying to set up a winery scene with a plexiglass grid as shown in the picture below.

 

My vray mtl is working as expected, except for the glowing side faces.

 

I think (correct me if i'm wrong) that the effect i want to achieve has to do with

(fog color-mult-bias, and or refraction exit color and or dispersion).

 

For simplicity and speed reasons i'm using

Refraction color: white

Amount: 1

Gloss: 1 (will lower it to 0.94-0.98)

Ior: 1.49

 

I did some research online and most threads about this matter are rather old and most recommend faking the effect using self illumination etc. I also read that in reality this effect is happening due to sanded and roughened sides of the material.

 

The question is, how should i approach this kind of situation in terms of light/shader interaction and rendering speed? One vrayMtl and experiment with fog and or exit color? Different shader to the glowing faces ? Or some king of coated material and uv mapped different values to the side faces?

 

Any help or suggestions will be very appreciated!

[Nicolai Bongard]

Your question made me think about an old project of bertrand benoit, there is a discussion of a similar effect, allthough it is the green color of glass visible on the edges - try reading the comment section here:

 

http://bertrand-benoit.com/blog/northern-light/

[Stephen Thomas]

If you want the faces of the glass to illuminate then the material will need to have some diffuse colour (i.e. not black)

[alexandroskapsalis]

Thank you both for your replies and help. I read bertrand benoit's comment on Northern Lights and he is using a fog color with a small multiplier (.1-.2) to achieve the greenish color in his glass. The brightness though is a result of clear refraction of a visible light.

 

What i'm trying to do is explained in this video

where the side faces of the plexiglass are sanded or etched in order to get a more even diffusion of the light in that faces because of the surface scratches.

 

So as Stephen suggested it looks like diffusion, but i don't think that a non zero diffuse color will do the trick.

Maybe a uv mapped refraction glossiness? The easy way but not physically correct could be a refraction exit color or self-illumination but i would like to avoid that approach.

[ahmeds]

You're trying to simulate 2 different materials using one shader. You said it yourself, the sides are sanded and therefore they have completely different properties to their previous state. You can achieve this using 2 separate materials with a multi subobject material.

 

For the large sides, I'm using a normal Glass material, black diffuse, high reflection and glossiness, and 100% refraction with full refraction glossiness.

 

For the sides, I've used the same glass material, but with 50% refraction glossiness.

 

[alexandroskapsalis]

My first attempt was to duplicate side faces and assign a simple diffuse 2sided material to get the backface light. But your solution is much more efficient without the need of extra modeling and more physically accurate.

 

One question though, is it different to use a blend material instead of just a refraction glossiness map?

[ahmeds]

I just saw your reply. For some reason I only got the email notification now.

 

For your question, it could work if all you're changing is the glossiness amount. But depending on your scene lighting set up it might not be enough, you might have to also mess around with other other settings like refraction IOR, diffuse colour, reflection colour etc. So having 2 separate materials makes it easier to troubleshoot and fine tune the material.