Noise after 50000 samples

[joshuamkerr]

I could use some pointers when it comes to noise in octane renders. I think I must have read every prominent forum post on the subject of specular noise but still don't have a viable solution.

The scene is quite large and features some distant streetlights, created simply with an emissive material and point light. The closer ones seem to be fine but the further away they are the harder to resolve the seem.
In honesty I don't know if it is a distance issue or perhaps something to do with them being viewed through a glass material. Whatever the issue it isn't solved with samples as high as 50000 (adaptive) and I can't wait 45+ mins per frame. I'll be at this for the rest of my life otherwise.

I'm not using the denoiser pass, it's too blotchy for animation in this case. I may use some post denoising but the render is too noisy to do this at the moment.

Here is the noise and beauty pass plus my Path Tracing settings. Hopefully there is a fix.




Path Tracing Kernel
Samples 50000
Diffuse 8
Specular 24
Scatter 8
ray Epsilon: 0.01
Caustic Blur: 1
Gi Clamp 5
Adaptive Samplin: true
Noise threshold: 0.12
Min samples 512

hot pixel: 0.7

[elsksa]

Hello,

Sampling / Render Settings is, first and foremost, scene-dependent.

It would be recommended to share a screenshot of the Octane Render Viewer in order to help us have a more precise idea of how the scene is. The "image" and "image" did not (up)load, apparently.

I would gladly look deeper into the struggle you are facing, however, I would like to, in the first place, point you out to some fundamentals informative content.

• It is, always, strongly recommended to not only consult but also acknowledge the informative content from the official documentation: https://docs.otoy.com/Portal/Home.htm
• I have wrote a work-in-progress page about Octane's Render Settings: https://www.elsksa.me/scientia/cgi-offl ... r-settings
• Scene scale, proper shading and proper light intensity have a high importance in regard to sampling.

I have realized that this forum thread is under the Unreal Engine category. Is that correct?

[joshuamkerr]

Hi Elsksa,

Thank you for the response, your article was well written too, very informative for sure.
I do often turn to documentation first and do a lot or reading and research before posting.
Your article mentions inspecting passes to see which is causing noise so I will take a look at this and post my results.
It is quite a dark scene and the scale is substantial but noise in shadows is acceptable, also GI clamping sits nicely at 5 without any adverse affects.

I'm not sure why my images won't attach either so I'll try posting them as links...fingers crossed

https://drive.google.com/file/d/1E5aIR7 ... sp=sharing
https://drive.google.com/file/d/1J3csB8 ... sp=sharing

Also yes I'm using the Unreal Engine plugin for this work.

[elsksa]

Thank you for the links. The second one took quite some time to load but it worked for both.

Regarding Adaptive Sampling, I have to ask as I do not know: did you set random values or did you tweak them as per the scene requirements? In case the documentation is not enough, there is this video that could help: https://youtu.be/dHTnaYjj3g4

It is a nice looking scenery.

• Is AI Light enabled?

• The PMC Kernel is a more efficient kernel for "complex light scenarios" and "volumetric scenery". I would recommend giving it a try. However, the PMC Kernel does not support all Octane's PT features - if your scene does not have an uncommon element, it should flawlessly render the scene as PT would.

• By scene scale, I meant if the scene's assets are scaled to their real-world values e.g. the character is roughly 175cm/ 1m75 (6 feet if you are in USA) and not 17.5cm or 175m. This is also valid for the camera. Anything wrongly scaled can results in various rendering issues.

• What are the light sources? Mesh lights/Octane lights? Texture based emission material?

Regarding GI Clamping, it usually do not make a drastic difference when the light sources are under-powered or naturally* dull (as mentioned on my web-page).
*low intensity light sources such as a single small wax candle.

Do note that I am not familiar with Octane for UE4. I can only assume that it is close to be the same as a 3D DCC plugin or Standalone, though.


As a DP and if I may, I would partially suggest the following:
• A car's windshield subtle environment reflection emphasize,
• In terms of light ratio, it is unbalance with the environment street lights. A more powerful/intense light on the character. In fact, there is a subtle light shaping the face nicely, already. An emphasize on it might improve the shot.
• If the character is on the phone, the viewer would expect it as a light source lighting his/her face.

Good continuation with your scene.

Looking forward to receiving an update here, with the above render settings suggestions.

[EvolverInteractive]

Turn your parallel samples to 1 for Path tracing.

[EvolverInteractive]

Also for such a scene your noise threshold is a bit high. Start at 0.02 and parallel samples at 1 and then come back with a photo.

[whersmy]

If the rays of the distant lights do not contribute to the illumination of the scene, you could try using a ray-switch, so they will only be visible in the camera and refraction. Here`s a scene where you can dive into. It`s not the same scene, but you can see how it could work optimizing the kernel and adaptive sampling. Actually it`s also a nice setup to experiment with bokeh. It renders fairly clean till 5000 samples. You can import the .orbx into standalone. I`m on Octane 2021.1.

Also you can try this:

You aren`t using the denoiser, but if properly used, the denoiser can work really well for these type of scenes.
Check "Fake shadows" in the specular material/window, so rays will ignore refraction + you don`t need caustics I guess.
Normal/bump/displacement maps on the specular material/windows increase rendertimes by a lot!
You can check Thin wall at the specular material to let rays leave the material right away. This speeds up renderstimes a lot.
Make sure the glass/window has a slight roughness.
Increasing the coherent ratio really speeds up rendertime, but make sure it won`t create artifacts.
The aperture-edge also affects the amount of noise.
Make sure the emitters are low poly.
Make sure the emitter isn`t surrounded by a glass bulb.

[elsksa]

whersmy,

You have made great suggestions. However, some of them are a compromise to the scene's "fidelity". To take with a grain of salt.

[whersmy]

Yes, for sure. It would take more time to test them all.

[joshuamkerr]

Hello All,

Thank you for the very interesting replies. I want to briefly share my findings when it comes to resolving the kind of specular noise that won't resolve witin a reasonable time frame.

The noise was remedied in two main ways with a few additional kernel tweaks.

1) increase the size of light radius. I did this for most lights but had missed a couple and they were causing big problems. If you have a lot of lights in your scene turn them off sequentially until you see the noise disappear, then dive into the light settings. Berar in mind I am taking about Unreal lights so you cant set samples on a per-light basis.

2) Check your materials. I had a couple of materials with very low roughness and very high specular values. This would be fine for Unreal, but not Octane. Toning these values down helped a lot.

3) Path Term Power. I felt that for some of my distant bokeh turning path term power a bit lower than default helped. I set it to 0.2.

Here is the rendered shot. It is just a test for a film so not by any means a finished piece of work.
https://drive.google.com/file/d/1MyX7jf ... sp=sharing