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I am trying to render a large number of glass sheets stacked on top of each other (42 to be precise)

I bumped up the transmission bounces amount to 50 just to be sure. set up a simple 'office' environment with some area lights and 3 white walls to have some interesting refractions. I am also using HDRI as a light source.

Is there some general shader that would work well with this kind of setup (stacked glass)? Do i need to worry about different interfaces (Glass to glass, glass to air)?

See below images for the materials and sample render.

Light paths settings

Light paths settings

Material on top side of the glass sheet (as you can see the difference is that i use 'Is transmission ray' instead of 'Is reflection ray', also i add an image with it's alpha as a factor, the image is a mostly transparent png image with some text on it) Material on top side of the glass sheet

Material on sides and bottom of the glass sheet Material on sides and bottom of the glass sheet

test render with above settings test render with above settings

I am aiming at maximum realism yet the glass still looks unrealistic and it is "dark" inside no matter how many transmission bounces i use, How can i improve it?

I attached slightly simplified scene so you can see roughly how i proceeded.

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  • $\begingroup$ For maximum realism you can try rendering with LuxRender it deals with glass much better than cycles. $\endgroup$
    – user1853
    Apr 29 '16 at 17:32
  • $\begingroup$ Is your office scene a closed space? Unless i misunderstood using an HDR image may be overkill or unneeded here if the rendered scene is totally indoors. Maybe it can save you some resources and processing power that can be better employed elsewhere. $\endgroup$
    – Duarte Farrajota Ramos ♦
    Apr 29 '16 at 18:02
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    $\begingroup$ For added realism you glass itself looks pretty good to me already, try working on the scene around it instead. Improve lighting, add some materials perhaps a bit of dolor here and there. Those things help increase the immersion, and help with the reflection and refraction. $\endgroup$
    – Duarte Farrajota Ramos ♦
    Apr 29 '16 at 18:04
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FIRSTLY, do you have photo reference? ;-) This render might actually BE really realistic, but your eye is fooled because your brain knows that it's fake. Also, photo reference will help you be specific about what changes to make.

The basic glass and transparent shaders aren't terribly realistic by default. You'll want to look into Physically Based glass shaders. It's a complicated subject, especially for Blender, but essentially you'll build your own shader with a transparent shader, a refraction shader (it doesn't do any reflection), and a glossy shader. You'll put these individual components together with mix shaders, modulating the factor on them with Fresnel or Layer Weight input.

The full details are a bit beyond the scope of this site, but searching for "physically based glass" should get you closer. Also looking at how people have built "fresnel glossy" shaders for Blender will be helpful because the principle is similar.

Here's a helpful link, for as long as it's available: http://www.chocofur.com/6-shadersamptextures.html

It would also be helpful to add a colored checker pattern and/or noise pattern behind and under the glass just for production, so you can see what's going on a little more easily. Then remove it once you get everything right. These stark white, grayscale environments can be very tricky.

Hope that helps!

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  • $\begingroup$ Thanks Matt! It was a very helpful answer! My glass shader is near perfect recreation of Chocofur's glass shader, however I am worried that some settings would have to be different where the glass sheets "touch" (in my scene i left some space between the glass sheets for correct refraction calculations). I understand that the environment and lighting is what makes glass look real, hence that's why i put time into building something simple around it, the back of the room is open so some coloured light from the environment map gets in. $\endgroup$
    – Wojtek Grabczak
    May 3 '16 at 9:00
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    $\begingroup$ You're right that where the sheets touch will be an odd case, but I don't know that there's anything you can do about it in the shader. Maybe, but I don't think so. I'd also recommend that in Light Paths, you crank everything up to the max 128 (aka Full GI). Turn on "Progressive" in the performance section and just let it render for as long as you can (overnight). Sometimes "problems" are merely the result of not doing enough calculations. $\endgroup$
    – Matt
    May 3 '16 at 13:13
  • $\begingroup$ ...and it'd be nice to see an update, if you have new images ;-) $\endgroup$
    – Matt
    May 3 '16 at 13:13

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