Interior denoising struggles

[joepr]

I'm using Octane now with great satisfaction for the last few years to create architectural visualizations.
Exterior scenes render really easily noise free in a very short time. It's fantastic.
However, I have difficulties creating noise free interiors where there is limited 'natural' light hitting the scene. I tend to have designs with dark walls and ceilings which does not seem to help either.

I know there have been many similar posts regarding (de)noise. But I can't figure out what I might be doing wrong.

My work flow for interiors and exteriors are the same. I use the following settings:
- Environment tag HDRi maps (up to 24K) as primary and secondary environment
- Octane sun mix texture
- all interior lights coming from light sources are emission texture black body based materials
- Kernel: Path tracing
- Max samples: exterior 200-300 samples (always sufficient), interior with plenty of HDRi light 500-800 samples (usually sufficient), interior with little to no HDRi light 1500-2500 samples (not noise free)
- Diffuse, specular, scatter depth: as low as I can bring it without changing the feel of the image or killing reflections. Around 8-8-8
- GI clamp: 1, but I try to increase it on interiors to see if it brings a visual better result
- adaptive sampling: noise threshold: 0.03 and min samples 100
- ACES tone mapping (out of the box Octane, not setup myself)
- Usually set up my exposure by adjusting the HDRi power to match something I like with camera 'exposure 1' for the exterior. For example my HDRi has a power of 6.0
- I adjust the exposure of my interior scene with the camera imager tag to for example 7 up to 25 for a very dim scene. I honestly have no clue if this has impact on the quality output of the render engine as opposed to increasing the HDRi. Would love to know!
- Spectral AI denoiser. I make sure to also have the use denoised beauty pass option.

My exterior scenes render in 5-10 minutes with great results. The dimly lit interiors take 1 hour with unacceptable results. Obviously I can increase my max samples a lot. I'm eager to find out if improvements can be found elsewhere. For reference, I'm using a RTX3080.

I have attached some samples of the noisy render before and after denoising from a work in progress. Furthermore, two finished renders of the same file, same model and same materials but one in a dimly lit scene vs one which enjoys more environment light. The output of the brightly lit scene is satisfactory to me (and took half the render time).

Appreciate any suggestions in work flow or settings to get cleaner and quicker results!

[ShivaMist]

I would suggest a few thing that you_ didn't try :

- Setup your lights with the a Sample Rate value :

Sample Rate

The sample rate determines how many samples will be used in the shading of the light being cast. In some cases, there may be more than one light in your scene, and some of them may create noise in a certain area. In such cases you can reduce noise by defining more samples for a given light. However, you may need to set the sample rate of other lights when doing this, because this option works as a "ratio". You can think of blackbody emissions on the scene as "sample weighting". In the example you see in the picture below, "Light A" has 10x more samples than "Light B". The default value of 1 works in most scenarios. It is recommended to keep the default value unless you use different lights and noisy situations.

- Use IES lights to have more control on the amount of light instead of having the disc emmitting at full throttle

- Multiple light pass rendering that you combine in post, not really an elegant solution but that works (Seperate all lights that take too much time to render and optimize them in a new scene/take)

[joepr]

I would suggest a few thing that you_ didn't try :

- Setup your lights with the a Sample Rate value :

Sample Rate

The sample rate determines how many samples will be used in the shading of the light being cast. In some cases, there may be more than one light in your scene, and some of them may create noise in a certain area. In such cases you can reduce noise by defining more samples for a given light. However, you may need to set the sample rate of other lights when doing this, because this option works as a "ratio". You can think of blackbody emissions on the scene as "sample weighting". In the example you see in the picture below, "Light A" has 10x more samples than "Light B". The default value of 1 works in most scenarios. It is recommended to keep the default value unless you use different lights and noisy situations.

- Use IES lights to have more control on the amount of light instead of having the disc emmitting at full throttle

- Multiple light pass rendering that you combine in post, not really an elegant solution but that works (Seperate all lights that take too much time to render and optimize them in a new scene/take)

Thank you very much for taking the time to respond.

I set up the sampling rate for the black body emission from the default 1 to 100. Not sure if this is about the value one would recommend. Might need more boost?
It does give me some improvements, most noticible around the bright area the emission is shining on. But not what I was aiming for. The result is attached.

I never got around to play with IES lights, but I'll definitely give that a shot asap. From a creative perspective this will increase realism a lot as disc emitting does not really represent acutal lighting distribution.

[ShivaMist]

I think IES lights will help a lot for realism, which is quite important in your case!
On the subject of the sampling rate, you can try to boost more the value, but i don't think it will help more than it already is.

With an afterthough, i have a more few points that you can try to further optimize the scene :

- If you are using the Pathracing Kernel, try to bump that Caustic Blur to 1.0
- Check if in your materials that you are not using a value of 1 for the Specular, it can cause some longer sampling/and create strong caustics which are hard to resolve the Pathtracing Kernel, you will find some more advice here : https://help.otoy.com/hc/en-us/articles ... for-Octane
- Try the Photon Tracer kernel, i think it's quite useful in archviz because you can get these realistic caustics from your materials https://help.otoy.com/hc/en-us/articles ... ing-Kernel

[elsksa]

I set up the sampling rate for the black body emission from the default 1 to 100. Not sure if this is about the value one would recommend. Might need more boost?

Sample rate isn't a light-sampling parameter (as in some other renderers). This page has some more information about it (and recommendations).

Regarding the denoiser, the ideal situation is when the scene is as optimized as possible, which is where ShivaMist was heading.

[joepr]

I think IES lights will help a lot for realism, which is quite important in your case!
On the subject of the sampling rate, you can try to boost more the value, but i don't think it will help more than it already is.

With an afterthough, i have a more few points that you can try to further optimize the scene :

- If you are using the Pathracing Kernel, try to bump that Caustic Blur to 1.0
- Check if in your materials that you are not using a value of 1 for the Specular, it can cause some longer sampling/and create strong caustics which are hard to resolve the Pathtracing Kernel, you will find some more advice here : https://help.otoy.com/hc/en-us/articles ... for-Octane
- Try the Photon Tracer kernel, i think it's quite useful in archviz because you can get these realistic caustics from your materials https://help.otoy.com/hc/en-us/articles ... ing-Kernel

IES helped quite a bit on the noise! Furthermore, it reduced my render time from 60 minutes to 26 minutes. So I can comfortable increase samples to get an even cleaner result. Last but not least, it looks much more realistic. Good stuff and fun to play with different IES files. I've attached the improved image.

Changing Caustic Blur from 0.5 to 1.0 increased render time from 26 to 30 minutes without removing noise.

My materials don't have a specular value of 1. Most of my materials have either a specular map or float value around 0.5

I heard about the Photon Tracer and the "1000 times faster caustics" and gave it a shot. Render time went to 1h15m with similar settings. No improvement in noise. I guess Photon Tracer is usefull when caustics are involved (not in this archviz)

I set up the sampling rate for the black body emission from the default 1 to 100. Not sure if this is about the value one would recommend. Might need more boost?

Sample rate isn't a light-sampling parameter (as in some other renderers). This page has some more information about it (and recommendations).

Regarding the denoiser, the ideal situation is when the scene is as optimized as possible, which is where ShivaMist was heading.

Thanks for joining the discussion and referring to a very insightful page.
Do I understand correctly that a sample rate of 2 already prioritizes that specific light emmiter? So it's not important to have it at any higher value. When you create more complexity, it might be useful to rate it 4 in order to give priority over a 3 light source?

I do agree on scene optimization. It's a thing I do for materials, objects, instances, polygon count etc. As you can tell, I'm fairly inexperienced with (interior) light optimization. Therefor it's a bit of a broad topic how to achieve optimal for lighting. If you have some practical examples, I'd love to hear them.

[frankmci]

Thanks for joining the discussion and referring to a very insightful page.
Do I understand correctly that a sample rate of 2 already prioritizes that specific light emmiter? So it's not important to have it at any higher value. When you create more complexity, it might be useful to rate it 4 in order to give priority over a 3 light source?

The sample rate is just a ratio, so the specific numbers you use doesn't matter. If you use 1 and 2, then 2 will get 2x the number of samples than 1 does, exactly the same as if you used 50 and 100.

You can use whatever number range you are comfortable with. I like to use 1-100 with 100 being the most important, most sampled light sources, with all others being some smaller fraction of those. With really distant or very small lights that are visible, but don't noticeably illuminate anything, you can turn off "visible on diffuse" and, "visible on specular," to essentially set their sampling to zero, speeding things up and eliminating any possible noise from them.

If much or all of your geometry and lighting are essentially static with just a moving camera or the like, it can totally be worth baking all or some of the illumination once you like it for a tremendous reduction in render times.