Why do I have a large white artefact on the rendered image? [duplicate]

Cant figure out why the rendered image has a large black and white artifact (on the bottle on the right)?

This is the blender file.

Appreciate any tips!

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• it doesn't happen when I open your file in 2.79 or 2.8 – moonboots Mar 18 at 14:46

That big error on the top is caused mostly by Fireflies and how the denoiser works.

The denoiser has a hard time dealing with small bright elements surrounded by darker pixels, as is the case with fireflies, and creates new artifacts instead.

Just for comparison here's the image with the same number of samples and no denoising (those random bright pixels are the fireflies):

For other examples see: How to properly denoise renderings?

What is the solution?

You need more samples and less aggressive settings for the denoiser

Or get you can get rid of the denoiser completely and use some clamp indirect to control the fireflies.

But you can also avoid those hot spots and fireflies if you change the lighting on the scene.

Don't use point lights, or very small lamps, to light shiny and transparent objects...

They will be reflected as bright shiny points on the surface and are more likely to cause fireflies.

If you use large area lights fireflies are less of a problem. Here's the same scene at 600 samples, no denoising and no clamp indirect.

For tips on how to light shiny objects read:

https://blender.stackexchange.com/a/50576/1853

Other advise. Try to avoid high levels of subdivision (like you have in the plane used as the background). You are generating a very large number of unnecessary vertices by setting the subdivision to 6. Very rarely you would need more than 3.

Last piece of advise: Try to make your objects to the size they would be in the real world. Your bottles are larger than a house at 9m tall. It makes a difference in terms of the size and intensity of the lights (and if you are going to do any kind of physics or fluid simulation), and also in terms of the depth of field on the camera.

• Thanks a lot! This solved the problem. – Sophia Malakhova Mar 26 at 6:35