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first time posting here and very new to blender, Im following BlenderGuru's latest tutorial and I'm having some issues with volume absorption, this is of course not a job, I don't have a deadline, so I wanna know what is wrong with it and how to fix it not just do it in a different way.

I rendered each picture at 128 samples using denoiser with cycles in blender 2.80, I'm not sure the exact value I applied to the volume as I changed it a lot to check different results and they were all basically the same, with that foggy look, however it should be at around 700 for this one.

One thing I noticed is that the material looks a bit different in the material preview than in the last picture here where it looks opaque on the sides while in the preview it looked glossy

In the first one the water is the same material as the cup, so you see there shouldn't be an issue with the geometry

Edit: Just found a way to add the blend file so is easier for you to check http://pasteall.org/blend/index.php?id=52500

in this one the "water" material is the same as the cup

here I added the volume absortion, just simple as the tutorial said (no nodes)

and here i separated them to check if there was an issue with the volume or the glass material

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  • $\begingroup$ Do you have two intersecting surfaces in the fluid content zone? See blender.stackexchange.com/questions/35726/fluid-in-a-glass which I think this question is a duplicate of $\endgroup$
    – Duarte Farrajota Ramos ♦
    Commented Oct 22, 2019 at 11:03
  • $\begingroup$ Yes the liquid volume intersects the cup volume a little bit, when they don't it looks weird, with stripes in it so is easy to notice and fix, however in that post you showed me they talk about a different method and sorry that's not what i'm asking for, I followed the geometry/volumetrics method and is not showing me the result that blenderguru's and other people get, I was mostly wondering if there is a default option I'm missing or if it's in fact an issue with drivers but the first picture where I'm not using volumetrics and the top of the coffee look perfect so I doubt is drivers. $\endgroup$
    – 5U3M0R
    Commented Oct 22, 2019 at 12:20

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I was facing the same issue when doing the Blender guru tutorial. I tried searching in a lot of threads for multiple hours but did not find a solution that worked. Then, I found an alternative method from a blender StackExchange thread that worked quite well for me. It talks about tweaking the IOR values of the faces of the coffee which face the glass. The link for the thread is given below -

Liquid IOR

Image before tweaking the IOR value- Before tweaking the IOR value

After tweaking the IOR value of the coffee faces by following the solution in the link and setting it to 0.8- After tweaking the IOR values and setting it to 0.8

IOR set to 0.91 based on the formulae used in the link- IOR set to 0.91 based on the formula

You can play around with values further to get the desired look.

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The default light bounces for Volumes is 0.

enter image description here

This is a pretty terrible default, in my opinion, because it causes a couple of issues. One issue is that whenever the volume is behind another shader in the scene, the ray is reported as lost. Observe that this shape should be colored blue inside.

enter image description here

If we raise the Volume bounces by just a couple, we start getting the expected results.

enter image description here

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I have an answer I noticed just now, (I'm also learning from Blender Guru) I just deleted the glass material (the glass of the cup stayed) and the liquid was grey-blueish color, and I added the transmission and it was un-transparent! (it was black!)

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    $\begingroup$ Hi there :) Can you make the answer more clear? It's hard to understand what you are conveying from the current answer. Keep the answers detailed and simple as possible. $\endgroup$
    – Nxdhin
    Commented Aug 16, 2020 at 6:52

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