Fireflies in interior rendering

Started by PerFotoVDB, July 02, 2020, 04:52:10 AM

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A) Why do interior arch viz style renderings cause so many fireflies? Even rendering at 2048 or 4096 samples don't fix the issue.
B) Why is keyshot so incredibly slow in rendering this style renders compared to other renderers? A 4K (with dof) image rendered on our network with 256cores takes 8 hrs and it's not noise free. This is crazy.

Anyone having the same questions or tips to improve render speed and quality?
I have tried:
- increasing the samples on all materials
- rendering in custom control mode with every setting following the manual.

Any insights?


Eugen Fetsch

Propably your lights are to close to other meshes, or inside of glas objects. If you can shift them a little bit away from our otside the surfaces it should help. 



Thanks for the tip. However, I highly doubt this is the case. I have no window glass or any other glass in the office space I am rendering. They're all reflective, glossy and diffuse surfaces with dof. Even switching the dof off doesn't really help.
A second issue is the detail of the shadows or gi in concave's just horrible. I increased the shadow quality in custom control, switched off gi cache, added bounces 9this makes the render times even more ridiculous high),...

I can't show the complete image as this is obviously client work but I can show fragments.
Please see below for the problem areas.

Eugen Fetsch

Do you have caustics on? Can you share the KSP via PM so I can have a look on it?



No caustics on. Tried product and interior rendering mode with shadow quality 4, no ground illum, 8 ray bounces and GI on 2 or 4 depending on the illumination mode used.

Unfortunately, I can't share any production files. Which makes it really difficult for people to offer advice.

Could it be linked to the complexity of the dataset? CAD models often go over 100milj triangles.


Eugen Fetsch

Don't believe that it's about the polycount - I had 180 millions polys in a scene rendering 4k in 20 minutes completely noise free. It could be anything, even a strange material setup (high set bump maps, etc.). Can you share the scene without clients product? (If it's about the product in use). Place something different inside and PM the scene.

Otherwise it's too difficult to help.



Tnx. Currently on it with support.
Let's see what comes out.

Keep you posted


There is a workaround to remove the fireflies in photoshop if that helps?

I often get fireflies too and it annoys the hell out of me. but ive never actually been told why it causes it. I know a lot of emmisive lights can cause it but i often use area lights with high sample numbers as well as having high sample number in material roughness.


Thanks for the reply.

It's very frustrating to do to manually and even worse when doing animations.
Do your high samples on the area lights and materials (128-256s?) result in high render times?


Eugen Fetsch

Check out "Neat Video Denoiser" ;) ... or any other video denoiser, they might help you to get rid of the fireflies within seconds, without edditing every single frame manually.

On the other side, I've already said that fireflies can come from everything, even from to high set bump maps. If you could share a scene (via PM for example) I could have a look on it.

What did the KeyShot support told you?


Nice idea for the Neat video denoiser :)

Keyshot support was back and forth. In the end it looks like multi-GPU would help, although I have a 256 core cpu farm, change lighting and reduce resolution. I gave up... because I want that specific lighting and very hi-res.

Thanks for the follow-up.