What is Noise degrain filtering?

I just wanted to ask, what is a noise degraning filter, and the following charts that open after It's unlocked.

Noise degrain radius, noise degrain blur difference.

And what is the best way to approach this? 

Thank you very much :)

Comments

  • ebergerlyebergerly Posts: 3,255
    edited April 2021

    I can give you my general view of denoising in general and what it does. I don't think you'll get much clear definition on what the various denoise filters do since it varies a lot depending on your image and the methodology and a bunch of other stuff. 

    If you watch an Iray (or other raytracing) render, the first preview images might look like the image below. Noisy. Anyone who looks at it knows that there's a bunch of white speckly noise where it should be rather uniform and smooth. 

    The goal of the various denoising algorithms is to make the software able to recognize what to us seems obvious. Get rid of the noise. So how would you do it?

    Well, since every image is just a bunch of colored pixels, you could sample the colors of a bunch of nearby pixel colors and see if there are any outliers that don't belong. So where you see a white speckle in the image below you might say "well the 20 pixels surrounding it are brownish, not white, so clearly that one doesn't belong" and it goes ahead and re-colors the pixel. 

    Some more advanced techniques use a library of many, many "typical" images and compare the image with what seems typical from the other images, and using some fancy AI techniques it does some handwaving and comes up with what the pixels should look like. "Oh, that's shaped like a window, and from my vast library of window images it should look like this..." 

    Of course, it's all a guess, and the purpose is to make the image look good faster than it would take to do a full render. But one problem is that it depends on what algorithm you use and what settings you apply and what YOUR image looks like and a bunch of stuff. Which is why you won't usually find much definition on what the settings actually do and how to set them. Really you just need to try them out for yourself on your renders and see what works. Personally, I almost never use any of the denoising tools since I'd rather wait a few more minutes and get a better result than settle for the often poor (IMO) results from denoising.

    Also, some techniques do the denoising during the render, and some do it as a "post-processing" step after the render is complete. 

    Anyway, here's a section from the Maya Iray documents discussing the Degrain Filtering you're asking about:

    "Degrain Filtering can reduce low frequency noise without sacrificing overall sharpness. These are intended to be used in the final stage of the rendering phase, mainly to reduce remaining subtle grain in difficult areas of a scene.

    Note:

    Unfortunately there is no general recommendation on which degrain filter mode will perform best on a specific scene, thus it is necessary to cycle through the different modes manually to receive the best results for a given scene. As a rule of thumb, modes 3 and 5 are usually the most reliable ones, with 5 being the more aggressive of the two. Also note that the overall rendering performance can be reduced noticeably on low end CPU cores, thus the filter should only be enabled in the final phase of the rendering process."

     

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    Post edited by ebergerly on
  • SpaciousSpacious Posts: 481

    You've just discribed the denoiser.  OP is asking about the noise degrain filtering.  It's similar, but works on the individual surfaces instead of the whole picture.  Sort of decides which color reflects off which pixel to get ray traced bact to the camera.

    While the denoiser tends to remove details, the noise degrain filtering doesn't really.   You really do have to mess around with it quite a bit as most of the time it's effects are really subtle.

  • Thank you all very much for sharing a piece of your knowledge with me, thank you very much.

    I as well put some research into it as well, through taking a bunch of renders over and over again and trying out all of them one by one, but considering I'm basically running on a potato for a computer it took a much longer time for me to have all of them be rendered and reach my conclusion. And have to say it does an Amazing job against removing fireflies as fast as it's possible, and noise degrain radius should not be tweaked that much neither should the noise degraning filter cause it may give off the complete opposite results, by either not doing anything to the image or just replacing the noise somewhere else. I'd say a:

    2 or 3 for the noise degraning filter

    And anywhere between 3 to 5 for noise degraning radius

    And as for the noise degraning blur, it just adds a blur to fill in the spots, which means it's useless so it should not be touched at all, just leave it be

     

    And also knowing the importance of lighting, I think your generally speaking, the more light the better results for this option

    Don't use any noise reducing stuff in a scene packed with different colours 

    And in general use it if you have a potato computer.

    Here's what I gathered from this, once again thank you for your time :)

  • prixatprixat Posts: 1,585

    That's interesting information, what do you mean by "a scene packed with different colours"?

  • mysterioushawk.nmysterioushawk.n Posts: 21
    edited April 2021

    prixat said:

    That's interesting information, what do you mean by "a scene packed with different colours"?

    What I meant by that was, that if a scene has too many characters loaded in, or if the characters are put in a jungle of some sort, or a packed environment. a setting that would overcrowd the scene with loads of different stuff basically. Maybe only than can the noise degraning filter not work properly. Now this is only a theory of mine for now cause I currently have not tied it out yet.

     

    Post edited by Richard Haseltine on
  • FishtalesFishtales Posts: 6,038

    I have the filter on and set at 3/2/0.20 for all my renders. I have the Firefly Filter set at 1500 which seems to be the optimal for most of my renders and for those where the Firflies refuse to go I drop it down until they do, I just did a render the other day where I had to take it down to 500 before the last one went.

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