A LOT of noise and fireflies in interior scene

So, today I started experimenting with creating an interior scene in blender. I added a couple of objects into a scene, then cut out a few faces to make windows. When I tried to preview render it, it had a TON of noise. So I did a quick google search, and put portals over my windows (I’m using Pro-Lighting Skies for lighting). I thought that would resolve the problem, but when I rendered it again (this time with 2000 samples), it still had a lot of noise and fireflies.

Here’s the image:

I have two windows, one in the front and one in the back of the “house”. I put portals over both of these.

Anyone have some suggestions?

How are you lighting the scene (sun lamp, point lamp, mesh emitter, HDRI environment map?)

Unless something has changed recently - portals only works with HDRI environment maps - they won’t reduce the noise in a scene lit by sunlamps or mesh emitters.

I used Pro-Lighting skies, which is an HDR. I’m thinking of reducing the bounces, what do you think would be a good number?

Try some of these tricks:


use them

I did use portals, like I said in the original post. I tried increasing the number of samples to 5000, but it was still noisy!
Could it be due to the fact that I’m using Pro-Lighting Skies? I heard in another thread that it’s notorious for being noisy for interior scenes. Does anyone else have experience with this?

How large are your portals. I found they worked best when they were just slightly smaller than the window. I essentially placed the portal within the window as if it was glass. Also - i’m not certain - but I think the portal has to point in the right direction (i.e. the dotted line of the area lamp the portal is created from should be pointing into the room)

Also - does your window have glass in it (i.e. actual refractive glass using the glass shader) - if it does then that won’t be helping since your scene will be lighted using caustics. If you have used glass - try removing it - or replacing it with architectural glass.

If the tips already offered don’t work - you may need to post your blend file so we can take a look at what is going on.

I think I’ll post my blend file, but first I’ll try a few different HDRs to see if that helps.

What has definitely helped me with getting rid of fireflies, but I only do outdoor scenes so may not work for indoors, is to make all light sources “multiple importance”.

If possible, use a map with some overcast dimming the sun value. A clear sky with visible sun, unclipped or a clipped version (more common) upscaled to proper sun brightnesses, will tend to create fireflies and noise. Of course, this will also deteriorate realism.

Avoid having outside sun shining through proper windows. Instead, from the suns point of view, there should be no interaction at all prior to hitting the direct lit surface (floor sees sun without an actual window glass). Transparency+glossy shader works much better than a proper refraction+glossy (glass) shader.

Mixed indoor and outdoor lighting is a killer. Smaller lightsources as well. A sun in clear sky is only about 0.5° (kinda small, same size as the moon), whereas an overcast sky will yield a much bigger “bright sun area through clouds” (and dim it down). The downside is obviously less pronounced shadows.

So the idea is to render in passes:

  1. General outdoor lighting for GI effects.
  2. Specific outdoor lighting mainly for shadowing effects, GI and high sample count ignored. I haven’t tried this though.
  3. Small indoor lighting in a separate pass, or even in several passes. I’ve tried this and it works way better than everything at once.
  4. Combine the result in the end.

Can you please specify in more details the workflow how to render such scene in passes? I have the same issue with lighting the interior with single HDRi environment map… Plus, how to increase the amount of light inside without blowing out the picture seen in the window? Is using the sun lamp the way out?

Sorry, forgot about this one, but…
Easy version: https://www.youtube.com/watch?v=lpcYY3OX4g4
Advanced version: https://www.youtube.com/watch?v=Gq5YWSpvME8
Those handles rendering passes in terms of prepping for individual handling of noise and fireflies on different (combined) rendering channels.

If noise is still unmanageable due to combined lighting (especially combining numerous small and big light sources), you can simply output either one combined pass or separate passes on a per light (or per group of lights) basis and simply add them together in the end. You would then be able to filter (remove noise) from small lightsources on the diffuse channel (if that happens to be the problematic one) more aggressively than you would other channels and/or other light sources.

I tend to only deal with separating the different light sources and do a combined pass, as I’m not “tedious” (?) enough to work with all the channels in a single light pass individually (I’m lazy, but what I do don’t require it).

Many people in this forum have problems with noise in interiors lit by ProLigting skies. I don’t have the addon so I can’t tell if this is the problem but you should definitely check that. Try to use a cloudy HDRI like this: http://www.openfootage.net/?p=7252