Interior renders / noisy render.

Hi all.
I know, this is old subject but, I have a problem with noise with my render.
So the story is, that I’m making renders for my friends, architects. I have switched to Blender from 3dsmax and vray, well, because of the price.
Scene is not finished, but I wanted to check first materials and how it looks.
6000 samples, Bounces: 4max, 8 diffuse, 6 glossy, 6 transmission, 3 volume.
Lighting is just a HDR outside the building and I use portals in my windows. I have separate HDRI for lighting, and separate for outside view (thanks to ‘is camera ray’). The one for lighting is set to 60 strenght, and that was quiet max to not have clipping ( I checked it with false colors).All materials are Principled BSDFs with different settings and maps.
I use Filmic color space.
The problem is, that to have clean render, I need to use like 50,000 samples ( and still, it’s not super clear). Does anyone have any ideas how to make things better?

Here is example of render with 6000 samples:

And here it is with 45,000 samples:

Well, I’ve assisted plenty of photographers with interior shooting and I’ve never seen any of them rely upon “the light that was actually there.” One of the most memorable photos was shot at 2 o’clock in the morning on a new-moon night. I would light the scene, in this case (Cycles) using carefully-placed off-camera light sources that you use like “soft boxes” and be sure that the illumination varies across each surface.

In other words – “fake it, Ingrid.” Don’t try to rely upon a simulation of exactly what might happen if the only light was streaming into the window from the outside world. Put the light where you want it to be, and make it plausible and (so to speak, in this case) dramatic, not correct. Make the light work for you to convey what you want to say about this scene. Even if it’s just “an architectural rendering,” you want to make the viewer want to live there.

When you are explicit as to where the lighting is coming from, and that it’s not actually coming from far away or having to bounce many times, you’ll get much less noisy results much more quickly.

This looks like a textbook case for Blender’s new denoiser (getting rid of the noise that takes forever to go away is precisely what it is designed for).

  1. Use nenoiser.
  2. Use low-res HDRI + sun lamp for diffuse lighting, even LDR might do the trick depending on the scene. They clean up a lot faster than HDRIs containing a sun. Ever try the sky texture (for diffuse only?). Hard to control but pretty clean compared to HDRI.
  3. Even an area lamp slightly outside the window (+sun lamp) could replace a full blown HDRI.
  4. Using simplify, switch to AO after a couple of bounces, using AO factors like 0.1 or 0.25 with reduced distance.
  5. If you can, mix in bigger bright faces on the dark ones. Dark colors show noise better than bright, and more bright surface area might camouflage the problem (not fix it). However, if you’re working for architects, you might not have much to say in this matter.
  6. Turn off caustics if enabled, and make a utility shader “if seen by diffuse, reflect as diffuse”. The result will not be accurate or correct, but it will prevent energy loss caused by turning off caustics. You have dark walls, most reflections would come from the glossy component. Without compensation, the brightening caused by glossy component would be completely lost. Caustics require a ridonculous amount of samples to clean up.
  7. I don’t know how effective this is (or if at all), but I tend to turn off MIS for all surface materials not contributing significantly to the scene bounced lighting. So on for major surfaces like floor, ceiling, walls, major furniture, and important light fixures. Off for pretty much all else. This has worked for me, but it might be a placebo effect, I don’t really know what MIS is supposed to do.

For me, the intent on using Cycles is to produce a good looking image, but not always plausible for the trained eye. I wouldn’t rely on it for a full lighting “study”, mostly for the lack of transporting light via glossy component of materials.

If you do the advice of mixing with interior lights, do so separately. Doing it simultaneously will just add noise since more lights are competing for the samples (is my theory at least). Keeping it separate you can do interior samples at about a tenth, gain color and strength control without re-rendering. When you now start adding those two together, the interior lighting should brighten the image enough so to help camouflage the visible noise in the shadows.

But yeah, you’re asking Cycles to do something horrible here - indirect lighting only on dark surfaces where possibly only caustics would bounce the light.

Carl; turning MIS off for non-emitting materials will have no effect according to some quick tests of mine (in terms of both sampling quality and speed). Turning it off anywhere will only bring major improvements if it involves emitting materials and lamps that are not important and/or are easy to sample.

Also, learn, know history of Camera AKA “Photo Apparatus”, around which the whole PBR deal is based upon.
“Lighting” and “Look development” are subjects you could be interested in.

Use of MIS, it’s efficiency mostly depends on lights used. There are couple of combinations which don’t work as good. But for most cases & lamps it’s better to have it on.

Thank you, I’ll try that!

In terms of indirect lighting, isn’t all surfaces “lights” (given they reflect/bounce light and thus become a source of light)? The feeling I get is that if a dark/nonsignificant surface as MIS off and a bright/dominant surface MIS on, the noise from the dark will worsen and noise from bright will improve, thus help drowning the noise from dark and look cleaner overall.

So in a white room with dark furniture, the indirect from the bright room will look cleaner if I turn off MIS for the dark furniture. It’s like, given 100 samples, I have to divide those when tracing towards bright room and dark furniture, making the bright more noisy. Similar for light sources I guess (even direct light); An area light in the window will only get half of the samples if a nearby tiny insignificant candle flame also has MIS turned on. Or vice versa, if the tiny lamp is the most significant one, I’d probably turn off MIS for the window area light.

I’m just guessing and theorizing here, although I’m approaching optimizing my own scenes that way (maybe in complete vain :p). Tooltip reads “sample as light”, which is kind of why I’m concluding this way. Note that I’m usually also aiding indirect lighting using huge area lights and/or simplify/AO at a low setting.

Well, I’m an architectural photographer for about 10 years, and I don’t use lamps in 99,9% cases because I don’t like the effect of it. I take few shots, one for shadows, one for midtones, one for lights/windows and compose them. It just looks more natural to me.

Well, yes, but before denoising, I would like to have a minimum of the noise, because from my tries here with different values of denoising, still, I need to use something like minimum 20000 samples, to remain details where I want them to stay, and don’t have noise.
@CarlG - thank, I’ll try that.
I can’t change colors here or anything in here. The project is not mine and I’m just making renders.
Thank you all for comments, I’ll try to improve it. :slight_smile: