Interior Lighting Experiments

[Daemoc]

I have been playing around with interior lighting and I am kind of lost. The default settings for most renders looks good enough when using HDRI's as lighting with exterior shots, but the interiors are a completely different animal. There are just too many settings and testing these settings can take hours to render.

I have been at these for days...

Is it better to leave the light values close to 1 and adjust the exposure to achieve the lighting you are looking for? Or is it better to leave the exposure at 1 and adjust the light value? Is there any real meaning to these values or are they completely arbitrary?

I am going for a nice balance of realism and speed. Anyone out there have any tips or general guidelines to follow using Falcon and interior lights? Maybe a lumens to Cheetah light value equation?

 

[3DSimulant]

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I'm also lost with light settings, but in this case I'll choose pic 2+3 as the realistic ones.

 

[Hasdrubal]

First off, it's photography that's recreated, so a lumens to light value would help marginally at best, because photography loses a lot of light, depending on the camera (the sensor, to be exact), the lens, iso settings (and maybe exposure, which is an additional setting in some cameras), aperture, actual light situation and where it's set up.

The exposure in Renderers is the overall setting like the ISO in a real camera. With some 100 iso you would get something like picture 1, except that even a weak neon light would contribute more to the light situation (not that much, though). And that's all, with exposure you change the way how the camera interprets the power of the light sources, but don't change 'em. If you have several of them and you want to keep the relative proportion of the different light sources it's better to change exposure. But you could and would get the same result with changing all light sources. With something like ISO 800 you would get something like pic 3 (maybe that would be less dark), with 1600 iso pic 2 (which is overblown). It's the overall setting you usually don't need to change because you build up your lighting with light source after light source. (In some apps it's a post-effect, so you can change the exposure after the render. You could do in photoshop (almost) as well).

Secand, Falcon doesn't like the legacy lights, so everything else than HDRI or an Area light does help you the least ( . And it's even worse: The neon light here (which would give a real picture a green color, by the way) seems to be an emissive light, which doesn't really contribute to the lighting of the scene at all. In other apps you could change the mesh itself to a light, but here you can't. You can cheat with an area light in the right position (not visible, of course). If you already did that, it need's to be stronger, because it looks like only an emissive light to me. So you use the area light and the emissive channel of the material at the same time.

The rest ... How would you photograph such a scene in reality? You probably would set up another light source (with the in-built flash it would look horrible, though), so you get more light into your scene. That's what's needed with a real camera, even for something like pic 2, where an additional light would make the whole image a bit more balanced. All those beautiful images we see on a daily basis, be that a professional advertisements or art, as well as movies have such additional light sources which make the picture in reality less realistic. But our eyes are accustomed to this kind of photography / filming, and if those wrong lights aren't there, it looks amateurish to us. It's the way we're trained to see pictures.

In this case, if you changed the neon light into a real light, you absolutely need some front light, because otherwise the back of the character would be more in the shadow. You could set up a bit are light (or have a white wall that reflect light, but that's maybe not strong enough, and ideally you would model everything that's not seen as well ... see below).

You could also use the scene like a stage and light it with an inside hdri of a bathroom which, provided you got a fitting one, would give you the most realistic render. Because in that bathroom there are in reality a lot of other things, like a tub that somehow influence all the reflections. There are many differences in hue, saturation, shadow and whatnot through all those unseen objects.

Whatever you do, those additional light sources are not natural, so should be used subtle, till you get the result you want.

For the window ... well, if you have a closed room, you could use a hdri, if you use an open stage, an area light would be enough, especially as what we see is anyway overlit.

With lighing you can't go wrong if you do more or less the same as you would do with a real photograph if you had an unlimited budget for flashes and reflectors (oh, well, you can chaet a bit more in 3d), and the best tip is in the end to get a book or two about lighting in photography. But even then it's not that easy, and at least I struggle all the time to find that small window between realism, fastness, 3d-ish look and what I actually had in mind.

 

[Daemoc]

Thanks Hasdrubal. I know a little about photography, and a stress the word “little”, but even with that knowledge it does not seem to help much with these Cheetah settings. I saw the camera does indeed have a lot of those settings but they only seem to apply to motion blur. They made no difference in lighting exposure.

There is indeed a small area light with that florescent fixture, but you are right, I must have missed turning it on in that first image. There are also four 6” LED dome lights (more area lights) on the ceiling which are not in view.

I am not even worried about composition or aesthetics yet, just trying to get something that looks somewhat natural. Once I get a baseline down I will definitely have to do more research into this aspect of photography though. This is one area I have a lot to learn. I should also note that this particular scene is just a combination of models I threw together for testing. The majority of the bathroom items are from my home remodel project, the room itself is just a quick sketch and the character was from a game I have been working on. This all started when I was planning on baking lighting into textures for an interior model and quickly learned the lighting was not going to be as simple as adding a HDRI image.

It looks like this is going to just take a lot of experimentation. And to be honest, I rather like experimentation for the most part. The problem I am having here is just the time it takes to do the experiments. These render times are brutal.

Speaking of which, I have been at this all day again today. I still have no idea what I am doing, but I have learned a few things. I am going to document this stuff as I go just in case someone else finds this useful.

First and foremost: Render threads.
This one really through me for a loop. I have been using all, (see 0), threads since we have had the option and never thought there would be any reason to change it. Here I have been abusing my poor iMac for no reason at all. Hours and hours of 100% CPU usage and insane fan noises.

I started doing testing with less threads and found that when I used 4 threads instead of all 6 my fans obviously do not get nearly as loud. “Well no crap Sherlock”, but here is the kicker. The same render only took 10% longer to render rather than 33% like it should have been. The speed differences are more noticeable on really short <5 minute renders, but the long >1-2 hour renders I have been doing really starts to close that gap.

So this thing must have been thermal throttling itself the entire time. I know Apple does not prioritize cooling on all of these fancy overpriced products in creates, but it should at least be able to run under full load without thermal throttling.

Really long story a little less long, the extra load and heat may not be worth the little time it saves. An extra 12 minutes on a 2 hour render is worth it to me when my iMac does not sound like a jet fighter in full afterburner. This has to be a lot easier on the expensive hardware as well right? Another added bonus is being able to do other light work as it renders without slowdowns.

Second: Render samples and brightness.
This is another one that really caught me off guard. I was doing all of my light testing at 100 samples thinking I was getting a good idea how things would look before a “final” render. This was not the case. The same scene at 250 samples is almost twice as bright as it was at 100. Although the lighting difference really starts to diminish after that. The difference between 500 and 1000 samples is hardly noticeable. I should note this is more prevalent with low light and high exposure settings.

Third: Light value vs exposure. There is one key difference. When the actual light source is in view the higher exposure setting seems to blow out the light in question. If you are going for a light that “glows” in the shot go for the higher exposure. If you are looking for a more subtle light, like a florescent light in a well lit room, go for the higher light value and lower exposure.

The exposure really works well with the sky light. Even with insane light values on the sky light at the default 1 exposure it just does not have the correct lighting effect. With a higher exposure it looks a lot more like actual sunlight but it also blows out the other lights on screen. As you can see with the florescent light that also has a light value of 1. My next test is to leave the Sky light at 1, changed the interior lights to a fraction 0.1-2 or so, and leave the exposure at 50. I am getting closer to what I am trying to achieve, but this is slow going.

 

[Hasdrubal]

The "neon" light in my eyes doesn't contribute very much in the other renders as well. So it should probably be a little bit stronger.

Render threads: That's awful, especially as overheating can damage a motherboard and processor over time. I don't know your iMac, but it's an overall problem with Apple. Noise is more important than performance for them, so the vents start too late and usually do too little. I'm not even sure if they work at full blast when fully running. But if the environment is somehow cool enough the alu casing and the fans should be capable of cooling so you actually could render at full speed and get what you were paying for. It's also help, if the computer isn't near a wall, and the air can stream around it (I saw this when with two identical iMacs one, not that near to the wall, was blasting away much earlier than the other). Anyway, you need https://crystalidea.com/macs-fan-control (or something like this). It gets obviously a bit louder when those vents kick in much earlier, but you get more power (and to be honest, reading about your experience, I'm just happy about the simple fact that I switched back to windows for 3d with a really good vent that's not even noisy, allowing me to use all 32 threads as long as it takes without a heat problem (for that a good motherboard is also of the essence). Anyway, fan control, at the cost of noise, should help you to get more out of your cpu because you have to control when the cooling starts to kick in. Also it helps the longevity of your gear. (But throttling isn't the only possible reason for such a thing).

Render samples: That would have caught me off guard as well. Though, I hardly ever changed exposure in Cheetah. To be completely honest, often I gave up to find the absolute correct lighting (just get the lights correct in relation to each other) and just do a little postwork, along with color correction. What I do for test renders is indeed to use the low settings in the beginning, really low, then when the scene is set up more or less find the settings I need, doing all this of course with a much smaller resolution then the result I want. When that small resolution really is rendered to my satisfaction, it's not often I find a reason to render the whole thing again at full resolution (sometimes there is some small error which after a four hour render really can piss you off, but my render times nowadays tend to be between a few minutes an an hour even with 4 to 6k resolutions). If you have a test render a quarter of the end resolution, for example, then you can expect 16times as much render time for the end resolution (displacement and other things, mostly not existing in Cheetah, can foul up that rule of thumb). Anyway, that's an error inside Cheetah imho. Shouldn't be that way (but it's maybe a situation where I just would change exposure).

Exposure: Like I said, I usually leave that alone. A small correction can very well be done in post. At least, if you create a linear output (i. e. an exr) there is no quality loss whatsoever, but you'll hardly notice it with 8-bit-pics. I'm often astonished how much information there is even in jpegs that can only be seen if you change exposure or whatever (usually in a situation with a real photo where I can't use that additional information is more a problem than anything else). Ok, lossless file formats (resp. jpeg at a 100 % quality) are important for that approach anyway. Also I never was able to create a realistic glow effect in Cheetah. That would also be something for post. The last render above looks better than I would have anticipated.

Sky light: It's still a legacy light that doesn't produce the best quality. Try it once with a hdr through the window and once with an area light, if you get a better result.

Except from that problem with more samples changing the brightness so dramatically it's actually the same thing over all the 3d renders out there (well, there are a few differences for the different render techniques, like biased and unbiased path renderers and whatnot). There is a video I already linked to once before (I think for Lydia) which could help you a bit (it once was a paid tutorial, but being older, he just uploaded it for free for all to learn from. The principles didn't change, though). Anyway, it's one of the 3d artists I really learnt a lot from, and he has that advantage of pronouncing english in a way that even non-native speakers understand him very well:

.

But as I said, there are a lot of others who created good videos about this (and tons of books and vids about photography).

 

[frank beckmann]

Challenge with interiors and unbiased renderers (uni-directional pathtracers) in general is how to get enough light rays through relatively small openings into closed spaces in a short amount of time. The answer is "portal lights" which "lead" light rays through a "tunnel/portal" placed in front of a window into the room for instance (and Falcon doesn´t have yet). Another thing often forgotten is IES light source profiles which instantly give a more "natural" looking lighting. In this scene I just use the SkyLight (which takes time to light up interiors) and an LED strip IES for the line light; shape area-rect light (which in most cases won´t be a neon tube but filament line lamps, because they do not require start/warm-up time, do not hum and flicker. A brand by OSRAM was Linestra which are now replaced with LED tech reducing power consumption from 60W to 7W for example).
I stopped at 1000 spp which takes 1,7sec per iteration for 1920x1440px.

 

[Daemoc]

@Hasdrubal
The neon light is there and you would notice the difference right away if I had the same render with it off. If you look at the characters right heel you can see the shadow created by the light. Also the character herself is a lot darker in the mirror with it off. But you are absolutely right. It does not add much to the overall scene with the sun. The sun is definitely doing the heavy lifting lighting the room.

Thanks for reminding me about Macs Fan Control. I have indeed used that before. There was a particular OS update that broke something with it many years ago so I stopped using it. I am sure they have fixed it by now. I will check that out again.

That Lighting For Storytelling vid is very informative. Thank you for the recommendation. There is a lot of good information here. Once I understand these lights a little better I am sure I am going to put this information to use.

@frank beckmann
I knew about the IES profiles, but I was just unsure about the legal stuff. Are these profiles made available to everyone free for commercial use? I will definitely have to dig into this either way. Even if I cannot use the profiles in my projects I could may be able to use them as a base line for Cheetah lights.

Your render looks very natural, but it has the same "morning" look to it that a lot of my early renders did. No matter how bright I made the sun, it just looked muted until I started messing with the exposure.

The portal light suggestion is huge though. This at least puts me in the right direction. I was so focused on the settings for the sky light trying to get it to light the room properly that I did not think to cheat the system. To be honest I wanted to do this without cheating, but these render times are going to force my hand I am afraid. I am happy with the direction I was on and seeing acceptable results, but the time it takes to achieve that was quickly getting out of hand. That last render was 2000spp and still looked horrible while the first one looked far better at 1000. I was thinking that the sample clamp setting might be causing the excessive noise with higher exposure, but you are right. It probably has more to do with the lack of light rays I am boosting with the exposure setting.

I am going set my exposure back to 1 and start boosting the sunlight at the main reflection planes with area lights. The only thing that worries me is shadows, but hopefully I can make the reflected light soft enough to light the room without casting harsh shadows. It's worth a shot anyway. I know I could boost the "exposure" in post like Hasdrubal suggested as well, but I am not sure how that would translate into baked textures. I'd rather not have to try and boost the textures in post as that could open up an entirely new can of worms, but it may come to that if this does not work out.

Thanks again gentlemen. I am off to render land for the rest of the day but I will post some updates tonight.

 

[misoversaturated]

In my view direct sunlight through a window is always brighter than a lamp light on the wall.
Using Cheetah3D sky light with default intensity I need to turn up render exposure to 10 in order to get enough brightness in the room.
The area lights above the mirror then get tweaked until the reflection of the guy in the mirror seems right.

Falcon without denoiser is just useless on my old MacBook Pro i7 CPU, I stopped rendering after half an hour.
Then I made a comparison with LuxCoreRender on the same Mac, LuxCore path tracer with indirect cache, Falcon with caustic filter.
Both render four bounces with adaptive sampling but without clamping or denoising, no filmic tone mapping.
Lux render stopped after 15 min, faster and cleaner (I was too lazy to apply all the texture maps on the character).
Cheetah area lights emit both sides and thus creates a huge glow.

Edit: Using Luxcore bidirectional path tracing (bottom image) with 0.8 gamma correction and some tint for the sun I get a closer match to the Falcon render, but need the same time (0.5h) for comparably noisy result.
Once Falcon gets a denoiser it will be usable for stuff like interiors, but not competitive because all the other renderers have a fast GPU mode.

 

[MonkeyT]

I haven't optimized for speed, but I have done a few tight interiors, so this sample contains a few tricks you may not think of. This scene has sky lighting for the exterior and a single point light and a single emissive object in the interior.


The room light is actually a pair of aligned cylinders: a skinny one on the interior which has a highly emissive texture that acts a filament, and a transparent outer cylinder that diffuses the intensity of the inner one. The emissive value has been set to a value greater than one by building it using a Color node instead of the material editor's color picker. Its intensity is set to 2.5, which might create a hot spot in a render, but I've diffused it by using the Transmissive Blur of the material on the outer Cylinder. This was enough to create the soft bright spot on the wall and light the vanity, but it wasn't enough to light the entire room, so I added a point light in the exact center of the cylinders.

This one relies upon using a Render Tag on both cylinders and deselecting the Visible In Shadows checkbox. Since I wanted the filament's lighting effects to be visible, I left it in the Reflections, Refraction and Diffuse render casting layers. Since I didn't want the filament to be affected by any lighting in the scene, I told it to not receive ANY effects from the renderer. The outer shell's visible casting aspects are entirely turned OFF except for being Visible in Camera, and I chose to let the outer cylinder receive all rendering effects except shadows -- though they could probably be turned off as well without any ill effects.

The point light is used normally except I set the Attenuation to None, which acts almost as an ambient light for the room, except that it will still cast shadows. To hide minor directional errors a bit, the softness value of the Light object may need to be set. Point lighting is also pretty powerful, so the Intensity value for this light is set to 0.25

The only other trick here is to remember that most interior ceilings are white, in order to bounce more light around the room.

-- one more trick I've used elsewhere: a large, white, flattened sphere can sometimes be used as a bounce reflector to redirect light into an area that needs just a little more soft light. Just use the Render tag to hide the object itself from the camera, shadows and refractions.


I hope this helps.

 

[Hasdrubal]

Once Falcon gets a denoiser it will be usable for stuff like interiors, but not competitive because all the other renderers have a fast GPU mode.

On a Mac it would be competitive enough, as really a lot of GPU rendering is only possible with Nvidia cards, and perfectioned for RTX at that. Even on windows there are enough people who don't want or can't play this game, as you need quite an expensive card with lots of RAM for more complex scenes (even with the rather new compression methods). And at the moment those cards are still kind of hard to get and / or overpriced. Also I don't know what influence ARM computers will have. All in all, CPU rendering is far from dead.

Denoisers on the other hand are getting better and better, killing less of that wanted detail than before (it helps, though, sometimes to mix the noisy and the denoised version in post). Meanwhile even AMD got a usable denoiser, working with A.I. They have their shortcomings, but you can end up with render times of a few minutes, even for high resolutions (5k and up). It depends very much on the scene, though, and there are still many situations where a denoiser is utterly useless.

But yes, a denoiser for Falcon would be a big game changer.

Also there is the visual quality, Noise aside, Falcon looks much better in my opinion than the two Luxcore results you posted. Although I found luxcore never that visually appealing to begin with. Do you use it also on Windows or do you use Cycles or Octane (with Blender I'd choose Octane, to be honest)?

 

[Daemoc]

@misoversaturated
I do use blender on occasion, but only for porting game content. I never tried rendering other than the realtime view port. I never heard of LuxCore until now. I have just downloaded it and I plan to play with it at some point, but probably not anytime soon. I hate dealing with blender as it is and the thought of learning an entirely new aspect of it might kill any ambition I have to continue working on this.

Those renders do look good though. And my PC outclasses my iMac by a large margin. I dunno, I may have to switch. I hate to, but I might have to.

@MonkeyT
That is some great outside of the box thinking. It always amazes me how different minds can solve the same problems in unorthodox ways. I will definitely keep these tricks in mind.

I have been at this pretty much all day again today. I have left the exposure setting at 1 and just tried different lights and values.

I am happy with the interior lights now. They are not perfect in these particular renders, but I think I have a good grasp of the light values, shapes and shades to accomplish what I need to.
Interior lighting @11pm


The sun light is still “noisy” but not nearly as bad as it was with the low light\high exposure. I have a single booster light where the light hits the floor and two lights outside of the window. (one with a slight green and one with a slight blue tint) There are some minor false shadows, but they are not as noticeable with a few interior lights on.
Exterior light only @11am


I have done 9000 of these today so I kept the samples low. All renders were set @250 samples and 1920x1080 with an exposure of 1.

Finally, I have a few other stupid questions. @Martin might know these...
1: The "visible in camera" setting for "area lights" does not seem to work looking through glass. I have my three booster lights all set to not visible, but the two outside of the window always show up in renders. I don't know if that is a bug, just a limitation with transparency or there is another setting I need to change.

2: There are some weird render artifacts on the walls where I cut the holes for the door and window. These walls are 100% flat, I made sure all of the vertices are welded. I have tried setting creases with normal breaks. Nothing seems to fix it. I know I can fix it with more polygons, but is that normal or is there some other issue here?

Thanks again for all of the information, tips and tricks gentlemen.

 

[MonkeyT]

1: The "visible in camera" setting for "area lights" does not seem to work looking through glass. I have my three booster lights all set to not visible, but the two outside of the window always show up in renders. I don't know if that is a bug, just a limitation with transparency or there is another setting I need to change.

Each light needs to be set to Raytracing + Transparency to project light through transparent materials ( They are set to Raytracing by default ). I, too, have noticed that lights set to "Not Visible" show up when viewed through a transparent material. I'm pretty sure this is a bug.

I seem to recall getting rid of it once by using a 2D Plane object instead of a 3D Box object as the glass window pane.

 

[misoversaturated]

Also there is the visual quality, Noise aside, Falcon looks much better in my opinion than the two Luxcore results you posted. Although I found luxcore never that visually appealing to begin with. Do you use it also on Windows or do you use Cycles or Octane (with Blender I'd choose Octane, to be honest)?

Since there is no progress with Cheetah3D and Macs regarding rendering for several years now (though Macs might come back with M1X/M2) I bought a PC with RTX graphics and learned Blender with Cycles, LuxCore and Octane (all free and usable on MacOS too).
I'm using Cycles for technical renders and LuxCore for Caustics. While Octane gives the best result, the Blender integration with online server connection requirement is a huge PITA and therefore I rarely use it.

I agree that the Falcon render looks best. The fast LuxCore version (really fast with RTX on PC) with indirect cache introduces light distribution bias that doesn't help this scene (sometimes it works better).
With LuxCore bidirectional which is strictly unbiased but CPU only I get closer to the Falcon result and could probably match it if I took two days time for tweaking. LuxCore sunsky is of course a bit different than Cheetah sunsky, only with the same HDRI it would be a fair comparison.

What LuxCore can do with interiors can be seen on their website gallery.

I still have a little bit of hope that the long hiatus will end and Falcon will get an upgrade with all those long missed features (no serious portrait rendering without SSS f.i.) but will I live to see it?

I do use blender on occasion, but only for porting game content. I never tried rendering other than the realtime view port. I never heard of LuxCore until now. I have just downloaded it and I plan to play with it at some point, but probably not anytime soon. I hate dealing with blender as it is and the thought of learning an entirely new aspect of it might kill any ambition I have to continue working on this.

Those renders do look good though. And my PC outclasses my iMac by a large margin. I dunno, I may have to switch. I hate to, but I might have to.

I hate Blender just the same though it has become much better over the years.
When modeling in Cheetah3D using PBR shader, it is possible to port a scene into Blender without much fuss (no physics or particles though, but those in Blender are more powerful).
There is a range of free renderers available including the not yet mentioned Radeon Pro, Appleseed and Renderman.
There the lighting needs to be tweaked which is different with any engine. Since Blender has a working live preview (not only in Eevee) setting up the lights is really much, much faster over there, I never do this in Cheetah because here it takes days instead of hours (think of how much time you already have spent on this).
All this can be done without leaving the Mac and in Blender you will only work on the render, light and material properties.

For speedy rendering which is indispensable for animations and/or high resolutions the project than can be opened on a PC with good graphics.

But like Hasdrubal just said, with just a denoiser in Falcon the whole hassle could be saved...

 

[frank beckmann]

2: There are some weird render artifacts on the walls where I cut the holes for the door and window.

Lower the Smooth angle and check if this helps.

 

[frank beckmann]

But like Hasdrubal just said, with just a denoiser in Falcon the whole hassle could be saved...

Not sure why this needs to be inside Falcon when for instance AffinityDesigner has a pretty neat noise reduction filter.
That´s the shot from reply #11 above.

When it´s for animation one can batch convert image sequences for sure.

 

[misoversaturated]

Not sure why this needs to be inside Falcon

Your example looks quite ok, but I wonder how it will deal with texture and bump detail this scene is missing, let alone stuff like fur particles?
Internal denoisers are superior because they have access to albedo, normal and geometry info.
Intel Open Image Denoise has become a standard like embree that is used by pretty much every renderer out there, saving users the hassle to go for external compositing.
But then again Cheetah3D doesn't even have any post editing tools...

I have been editing and denoising Cheetah3D renders in PS for years and are very grateful that I don't need that any more when using Blender, regardless the engine.

Martin had mentioned somewhere he was planning an integration at the end of last year but obviously it was delayed like everything else.

If one can find some hours of time for a final render there still is the possibility of leaving it to the adaptive sampling algorithm in Falcon which works very well with superior quality even the best denoiser can't match.

 

[Hasdrubal]

Not sure why this needs to be inside Falcon when for instance AffinityDesigner has a pretty neat noise reduction filter.
That´s the shot from reply #11 above.

When it´s for animation one can batch convert image sequences for sure.

I thought exactly the same at first, especially as the results with photoshop were superior to what I saw as examples of the more commonly available denoisers (the exception was maxwell's denoiser that works only with their renderer on nvidia gpus).

As misoversaturated already explained, the denoisers have access to the render buffers (color, normal and albedo. I'm not so sure about geometry itself, but all this is depending on the denoiser). Also they are specifically trained for 3d while all the other solutions, be that in Affinity, Photoshop or one of the more specialized apps, have video and photography in mind. All I know work with A.I.

That's why they (sometimes) work with very, very noisy renders. On their website (https://www.openimagedenoise.org) they have examples with 16 samples. I tried for example a scene with 64 samples and the intel denoiser. To get the same result, I needed more than 4000 samples without denoiser. Visually I didn't see a difference in that exact scene.

To get the same result in post, you'd probably need different render passes.

Looking at the first image on their website, you wouldn't guess how good they have become. Because that actually shows the downside, as it kills all the details and creates some blurry pulp out of the tree leaves for example. That's the first implementation. Now they have version 1.4 which has also some "pre-filtering" included, and that one seems simply awesome: http://www.cgchannel.com/2021/05/intel-releases-open-image-denoise-1-4/. It keeps really all the details in that example (I personally have not yet access to 1.4).

And we're talking about Intel's denoiser here. To my surprise they also support the new Apple silicone, and it's open source. Shouldn't be that difficult to implement.

And all that at the expense of one or two clicks and usually less then a second added to the render time.

Sometimes I do use different outputs (which ideally you would get with the same render) to blend them together or even paint that one part where it's killing (too much) detail. The reason is that those renders are too clean, and a little rest of noise sometimes is visually appealing (like the old film corn which we're accustomed to while the noise of digital photography usually is ugly as hell). Well, very seldom of course, I added a little bit of noise in post. (And usually I don't work in post more than 5 minutes or so, mostly used on quality control).

 

[misoversaturated]

Here is an 11min (200 samples) LuxCore render with caches, clamping and the new OIDN 1.4 which is already in Lux and would be awesome in Cheetah3D too
90% demonised +10%noisy

 

[ZooHead]

Here's some tests with one area light set to 10 or 20 with attenuation off using the "Fourth Wall" technique.
That is to remove a wall to shoot through which also lets light in from an HDRI light source.

I changed the HDRI image to change the ambient light.

I also added a slight pink tint to the area light for morning and blue for afternoon light.
Of course the shadows from the window are too soft with an area light.

 

[Hasdrubal]

(To create a stage was one of the techniques I recommended above ... There are a ton of free inside HDRIs available, even for bathrooms (you could for example find 2 on ihdri.com in "indoor": https://www.ihdri.com/hdri-skies-indoor/).