Weird artifacts in shadow when rendering transparent objects I'm rendering a transparent cup with water + transparent plate.
However, the right bottom part of the shadow seem quite off. It has artifacts in the shadow.

https://imgur.com/a/djoP72f

This is the problematic part


Before using the Denoising Data option in View Layer Properties, however it looks kinda ok. It looks like  this.

https://imgur.com/a/rX34dZl

So maybe it's a problem of denoising? However, this is part of the tutorial of Blender Guru's Donut Tutorial and he's using the denoising option and it looks just fine.

Here is the blender file just to be sure.





My sampling rate in the renderer is 128 and I'm using Blender 2.8. All the transparent materials are made by Principled BSDF, Transmission 1.0, and Roughness 0.0.
Denoisers use an algorithm to predict and remove noise (the fireflies). However, when your image gets too noisy, the algorithm will be unable to predict what is supposed to be where (remember it's looking at the pixels and running some sort of math to try and guess what you don't want in the scene, and how to use the surrounding pixels to fix it).

In this case, you're going to need to increase your sample count.