Reducing noise; a question of better lighting or higher number of S/p?

joey
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Reducing noise; a question of better lighting or higher number of S/p?

Postby joey » Mon Apr 04, 2016 8:04 am

I'm very new to Reality and have only started working with it a few weeks ago.
The software is great and the user manual extremely well put together and helpful. But even after watching a couple of video guides on YT and browsing forums reduction of noise is the one thing I have problems grasping.
For reference, here's one of the renders I'm currently working on:

Image

Here's a close-up illustrating the severe noise in the picture I'm trying to get rid of.

Image

The scene was set up in Poser with the most recent release of Reality (4.2). I've used IBL (specifically the MonValley Lookout sIBL set from a site Paolo referred to in one of his videos). The scene was then sent to a render farm, therefore I had to set a maximum amount of samples (6000 S/p in this case, rendered at 5000x3200). I've used the Agfacolor Optima 2 200 in the camera settings of Reality because I like the way that film interprets light (and thinking that an ISO of 200 should give me a clear enough picture).
What I'm trying to figure out is, whether I would have to add an additional mesh light (or 2) to the scene to get rid of the noise or if all it takes is another couple thousand samples per pixel. It's hard for me to just test and try different options because I'm running this on my Surface Pro 3, so rendering takes a lot of time. I was hoping one of you might have an idea how to deal with this efficiently.
Secretly I'm hoping that an increased number of samples will fix this, as I'm afraid adding a mesh light to the scene will completely change the look of it.
So what do you think? Does my scene need a mesh light in addition to the IBL (and does IBL usually need additional lights?) or should I just double the amount of samples per pixel to get rid of the remaining noise?
I'd be incredibly grateful for any kind of advice.

(Thanks for reading; hopefully this is in the correct section of the forum)

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Kimberly58
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Re: Reducing noise; a question of better lighting or higher number of S/p?

Postby Kimberly58 » Mon Apr 04, 2016 8:14 am

Is the IBL the only light source? Is it is that could be the issue I've seen this happen with my render, so yes I would add a mesh light or two and bring down the brightness of the IBL. Also setting did you use on the walls?

joey
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Re: Reducing noise; a question of better lighting or higher number of S/p?

Postby joey » Mon Apr 04, 2016 8:32 am

Wow, Kimberly, thanks for the super swift reply! Much appreciated.
The IBL is indeed the only light source. The walls (especially the figures' shadow on the boiserie panelling) looks weird, doesn't it? I've tried to simulate a plaster look using only a diffuse colour and a normal map. I've been looking around for a nice plaster preset or settings I could use for the material to achieve a plaster look in Reality, but couldn't find any, and I'm not well versed enough in Reality yet to create a plaster material myself without using a dirty old normal map :-/
Anyway, good to hear you've come across this issue when using IBL, too, and that adding a mesh light might help. I'll try that immediately.

pciccone
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Re: Reducing noise; a question of better lighting or higher number of S/p?

Postby pciccone » Mon Apr 04, 2016 9:12 am

There are a few issues to check. First, running on a Surface is not the right environment. PBR requires a fully-featured system, possibly a desktop-class processor with i7 processors. Even a standard, office-class laptop is not the best setup. The hardware is simply not powerful enough. When using limited hardware then it's imperative to keep the resolution low. At 5000x3200 you would be pushing a desktop-class machine. You need to lower your expectations with such limited hardware. 1280x720 would be more adequate. Maybe up to 1080p. I know that you are using a render farm but the Surface tablet is still acting as a bottleneck.

The pattern that you see on the wall is not really noise as much as the Sobol pattern. Try using the Metropolis sampler. Lastly, avoid using the film simulation except for the vary last phase, before saving. That is because the film simulation will add another layer of computation every time you re-render the image. That takes time. Instead apply it only at the end.

Hope this helps.
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Paolo

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fuzzy70
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Re: Reducing noise; a question of better lighting or higher number of S/p?

Postby fuzzy70 » Mon Apr 04, 2016 9:22 am

Sadly IBL's vary a lot, I have had identical scenes using different IBL's & some have cleared up quicker than others. The modes you use such as Mono-Directional or Bi-Directional along with what sampler Sobol or Metropolis can also have an effect of how quick noise will clean up. At a guess I would say your using the Sobol sampler from the pattern of the noise in your render although I could be mistaken. Adding a subtle mesh fill light could help or adding a plane as a reflector, however the latter can be awkward to align properly & takes some practice.

You could add another camera to the scene that frames the image the same as your cropped one & do test renders at lower resolutions with that camera to see what effect any changes to sampler or lights has in that area. Being a lower resolution it will render quicker, especially if it's small like the same size you have posted here as you can clearly see the noise even at that size. It is something I do quite often if I have problem areas as it keeps the scene intact & I can just focus on an area then switch back to my main scene camera for the final render, seeing as your final output is 5k x 3.2k you can understand a 500x500 render will be substantially quicker.

Another thing that could cause noise is your background prop, Lux really doesn't like pure white (255:255:255) & if you walls are that colour then you have a very good chance of noise. Not knowing your prop I cannot say if it has a texture applied to it or if it is just a colour, but changing it so it is just a single colour that's off white say like 240:240:240 (or slightly lower) may help & will not change the final look of the render that much. Again not knowing the prop in the scene that may not be the case.

Also I noticed that polygons are showing on the shoulder of the figures jacket. There are 2 possible fixes for that, adding a mesh fill light as mentioned previously can help eliminate that & you could add a level of subdivision to the jacket (may require another 1 or 2 levels of SubD but I would start with 1 first). That effect is a known problem with lights that cause quite sharp shadows, SubD helps & can sometimes cure it on it's own but otherwise adding a subtle fill light as well can also get rid of it.

With regards to the film type I don't think it makes any difference, my understanding of LuxRender is that it just renders the scene & things such as film responses are basically applied to the raw data Lux generates. The film does not or is not used in the actual rendering process but is an effect that is applied to the render data, the lights & their gains are what is used to generate the data & they are what determines noise (along with what sampler mode is being used). I would even say that the exposure controls don't have an effect on the raw data but are calculated on top as you can change the tonemapper options while in Lux & get a different output but still go back to one that you like the look of with no problems or changes.

Sorry for the long winded answer but hopefully there is some info in my reply that will help you get the result you are after & fix your problem.

Regards

Lee
Windows 10 x64, Daz Studio 4.9 x64, Poser Pro 11 & whatever the current version of Reality is :lol:

joey
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Re: Reducing noise; a question of better lighting or higher number of S/p?

Postby joey » Mon Apr 04, 2016 11:08 am

Thanks so much for the replies, Paolo and Lee.
The Surface actually has an i7 processor, but with only 8GB RAM it's definitely not ideal for PBR, I do understand that. I use the high resolution only for the final renders intended for print.
I haven't given the different sampler options any attention yet, so I will definitely switch to Metropolis as you suggested and see what the result looks like. Thanks a lot for the tip, that's really the last place I would have looked.

The white is at 243:243:243 so not quite pure but I will lower it anyway. Thanks for the tip. I have a prop in another scene that actually is a pure white, so I will definitely also have to change its value, too. I don't mind the slightly darker shade as that can be fixed later in editing.
Hahaha, I'm slightly embarrassed you noticed the geometry issue on the shoulders. I completely forgot about it when I posted the picture. This is not an issue with the jacket's mesh itself but an issue I encountered modeling my clothes on my figure in Marvelous Designer without having any level of subdivision applied to the figure. Any form-fitting or tight clothing therefore shows the geometry of the figure under it. I will have to fix that in Photoshop as well, and make sure to have at least some level of subdivision on my avatar the next time I use Marvelous.

Well I'm glad the film type isn't the issue here, at least. I guess I will work on lighting the scene better and then test the other sampler and mode, both you and Paolo suggested.

Thanks a bunch for the many helpful suggestions!! So glad I posted here! <3

joey
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Re: Reducing noise; a question of better lighting or higher number of S/p?

Postby joey » Thu Apr 07, 2016 2:19 pm

OK, I've tried a different lighting setup, specifically the Perfect Shot Scene for Poser that I downloaded from http://preta3d.com/downloads/perfect-sh ... -for-poser. I've added an additional (sharp) mesh light to the scene to achieve the shadow in the bg.
Here's the result after 7000 spp:

Image

Close up you can clearly see a considerable amount of noise. It looks almost noisier than the image i posted originally, while, at the same time, having upped the spp from 6000 to 7000.
Also, there's clear white spots all over the image.

Image

Image

Then there's these black and white dots of noise (?) almost forming a line:

Image

I just can't seem to get my head around this, especially since I used a pre-made setup. Do you think this lighting setup requires a couple thousand more samples to make it less noisy and get rid of the white and black dots or might the issue lie somewhere else? Maybe some of you recognize this particular "pattern" of noise (the lines of black and white dots I mean). I use 200 mm focal. Could that be an issue? Or is this a case of over-lighting, even though I've added only one additional mesh light to the original Perfect Shot scene? Ugh, I'd love to get it right and have a cleaner shot. Any ideas?

edit: The lines of white noise are even more apparent in the picture before I adjust the different lights in LuxRender to get the results above. See below:
Image

joey
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Re: Reducing noise; a question of better lighting or higher number of S/p?

Postby joey » Sun Apr 10, 2016 10:44 am

Just as an update, I finally managed to resolve the noise issue.
After reading about "dumb" and "intelligent" samplers on this site , the difference of the mono- and bidirectional type, and the recommendation to switch to "CPU - no acceleration" mode if I don't achieve the results I'm looking for with the default CPU Accelerated settings, I did just that and switched to CPU - No Acceleration in the scene configuration of Reality. Type: Bidirectional, FFs removal at 1, Metropolis sampler instead of Sobol. The results are staggering.

From this
Image
to this
Image

Every fine detail is clearly visible now without ANY noise.
Image

And all of this with a reduced number of samples (from 7000 down to 6000 Spp). I'm sure I can reduce the number of samples even further, but didn't want to go too low on my first try with these new settings.
The only question I have left is if just switching from Sobol to Metropolis would do the trick even under CPU Acceleration or if going with the non-accelerated mode and the appropriate Type and Light Strategy settings is the essential part here.

pciccone
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Re: Reducing noise; a question of better lighting or higher number of S/p?

Postby pciccone » Sun Apr 10, 2016 11:45 am

The non-accelerated uses the Bidirection integrator, which might be the right way of calculating rays for this scene. At this time there is no bidir accelerated.

Thank you for letting us know, I'm glad that you solved the issue.

Cheers.
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Paolo

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sigstan
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Re: Reducing noise; a question of better lighting or higher number of S/p?

Postby sigstan » Sun Apr 10, 2016 12:05 pm

Last edited by sigstan on Sun Apr 10, 2016 1:17 pm, edited 1 time in total.
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