Everything you wanted to know about rendering Glass not only with Cycles - Vilem Duha
Why Blender Stack Exchange recommends it
Blender Stack Exchange answerers point people to it when glass renders look dark, noisy, or shadowed wrongly, since it explains bounce limits and total internal reflection and how to work around them.
Recommended by 3 people across 8 different months, 2020 to 2023.
What it is
A roughly 30 minute Blender Conference talk by Vilem Duha on rendering glass in Blender, covering Cycles light path settings, bounce limits, total internal reflection, and tricks for glass-like materials. It is published on the official Blender channel.
What people said
Recommends impresso · 2020-04 · Blender Stack Exchange · on “Translucent vinyl plastic material”
[LINK] This is the setup I use for glasses, producing results such as the one above. It works by rendering the material as regular glass, except for lightrays that bounce too much (that is, more than three times), in which case it gets rendered as a simple green, transparent material. The Volume Absorption node is there to make sure the effect still happens when the sheet of glass is viewed from the side. You can adjust it to your own needs by substituting the Glass BSDF node for the one(s) you've so far been using and tweaking the colours to your liking. [LINK] You can check this and many other tricks for rendering glass-like materials in Vilem Duha's Blender conference, Everything you want
Recommends Allen Simpson · 2020-12 · Blender Stack Exchange · on “Two opposing faces on the x axis turn out dark, almost black in my material”
It may be that your object is so long, and your camera angle is such that a ray cast from the camera doesn't escape the object within the default number of bounces. Refer this video: [this video]
Recommends Allen Simpson · 2021-02 · Blender Stack Exchange · on “Is glass in Cycles just broken or am I doing something wrong”
also - [LINK] and I recommend this youtube video - [this video] the volume mix is very low and he can be hard to understand, but there's some good info here
Recommends Allen Simpson · 2021-04 · Blender Stack Exchange · on “Glass casting shadows and not looking real”
If you look at reference photos online, it does appear that glass casts a shadow of sorts. What happens is that some areas are darker and some are lighter due to refraction and reflection. [LINK] In blender, it looks like the default settings don't allow the full amount of light through, so I ran a series of tests. The scene is a simple drinking glass and a small area light. [LINK] I've raised Glossy and Transmission bounces to avoid any issues with total internal reflection a la this talk [this video] , but otherwise the first image is with the default settings. You can see the shadow is very dark. Unclamping Indirect Light and unchecking Filter Glossy both gave interesting results. Doing both a
Recommends Allen Simpson · 2021-05 · Blender Stack Exchange · on “Problem with getting a clear and smooth glass surface”
A couple of changes to default settings The Principled BSDF shader has a default Base Color around .8, which means glass will be a little dark by default. You can raise the base color to 1.0 for perfectly clear glass. These dark spots - [LINK] are caused when the light reflects internally a number of times that exceeds the number of bounces allowed in render settings. [LINK] Usually it's the number of Glossy bounces which you can change here: [LINK] You can learn more listening to this talk [this video] . To the model When modeling for subdivision it is often to your advantage to leave your mesh as low poly as possible, and let the interpolation algorithm do the work of placing the additional ver
Recommends Allen Simpson · 2021-09 · Blender Stack Exchange · on “Why there are black patches visible in fluid simulation?”
A couple of links - you might be able to work around by extruding the sides down, creating a bottom face, and using a Volume shader in addition to Surface. [this video] [LINK]
Recommends Allen Simpson · 2022-03 · Blender Stack Exchange · on “Does internally reflected rays count as refraction rays?”
They are actually Glossy rays for total internal reflection. Here [this video] is a relevant talk from one of the Blender conferences.
Recommends Geth270 · 2023-05 · Blender Stack Exchange · on “Is glass in Cycles just broken or am I doing something wrong”
Yeah, no. The default glass shader in Blender is just fucked and I can't believe it still hasn't been rectified after so many years (it's been like that long before I posted that question and still is). Results like you showed are possible but this is not the default settings. Really for anyone who finds this I recommend watching this video on how to deal with glass in Blender - [this video] It's no silver bullet but at least it explains the idiocy of Cycles glass and how to work around it. Physically based renderer shouldn't take mental gymnastics to render glass, IMO.
Cites fmotion1 · 2020-12 · Blender Stack Exchange · on “Strange Glass Reflectivity in Wine Bottle Scene”
I am testing out some materials and put together a simple wine scene from some downloaded assets. This is the render: [LINK] Anyway, there are parts of the render that look pretty unnatural. I've pointed them out here: [LINK] The wine glass bottoms are unnaturally reflective. They almost look like metal. There is some weirdness happening with the wine glass on the left. There is a lot of noise only in the wine bottle side where it is reflecting the wine glasses. Example of the noisy reflections I'm talking about (this is even after Optix): [LINK] Here's the glass shader I'm using for the glasses: [LINK] Here is my render setup and light paths: [LINK] I've deliberately cranked the Gloss, Tran