Cloud noise

[Kexikus]

Hi everyone,

I currently struggle with cloud noise in one of my renders. The scene is a sunset with one very simple easy cloud layer that I can't get free of noise even though all relevant settings that I know of are already pretty high and I tried even higher values with no changes at all. So I was thinking that maybe there is some setting that I just don't know about that could be the cause of my issues.

Here's what I currently have:
I use Defer All Shading
Micro Poly Detail: 0.6 (shouldn't matter though, right?)
AA: 10 with the Robust Adaptive Sampler at default settings (1/64th)
Voxel Scattering Quality: 100

Atmosphere samples: 32 (pretty sure that is more than I need)
Cloud Ray Marching Quality: 0.75

So far I tried increasing AA to 15, Voxel Scattering Quality to 300, Atmosphere samples to 64 and Ray Marching Quality to 2. All any of those settings did was to increase the render time.
Is there any other setting that might help in this case?

I'll attach a crop of the full render at the bottom. There isn't a lot of noise but if you zoom in you can still clearly see it in the darker cloud parts.



Thank you for your help!

[Kadri]

I don't have the newer build of Terragen and without the scene can't say much. Have you tried it with the soft pixel filter?
Just curious if it would help or not.

[D.A. Bentley (SuddenPlanet)]

Do you have Soft Shadows turned on in the Sunlight node.  Newer versions of TG4 have it turned on by default.  If so you could try increasing your soft shadow samples (Default is 4).

You could try increasing Ray-marching quality of the Easy Cloud to 1 or even 2?

The rest of your settings seem plenty high.  I never need to go higher than AA 8 myself.

Also under the Rendering settings Quality Tab there is the Edit Sampling button.  Whats your Pixel Noise Threshold set to?  It's a tricky setting because it changes depending on what you set your samples too.
When I choose 8AA samples it defaults to 0.0375, but I usually lower it to 0.0275 to get even less noise.

Hope that helps.  Let us know what you figure out.

-Derek

[Kexikus]

Thanks for the suggestions!

Soft shadows are turned off.

I already tried increasing the ray marching quality to 2 with no success.

The Pixel Noise Threshold is at 0.03 for AA10 but I just tried reducing it to 0.02 with no improvements either.

I don't have the newer build of Terragen and without the scene can't say much. Have you tried it with the soft pixel filter?
Just curious if it would help or not.

The "Cubic B-spline (soft)" pixel reconstruction filter or is it something else that you're talking about?

I'll also attach the scene file in the hope that this might help. Thanks again.

Korriban.tgd

[Kadri]

...

The "Cubic B-spline (soft)" pixel reconstruction filter or is it something else that you're talking about?
...

Yes that filter.

[Tangled-Universe]

I just had a look at your file and I just started some test renders, but I noticed one thing I feel I need to give some feedback on, which is your lighting setup.
You have 2 sunlights and they differ in colour and that 1 has glow in atmosphere disabled and the other one highlights on surfaces.
Apparently you'd like more yellowish light in the atmosphere and more neutral light for highlights on surfaces.
However...which highlights on the surfaces? There are no reflective shaders for your terrain so a separate light for this makes no difference.
The lighting of those 2 sunlight nodes isn't really separated either, since both still do light atmosphere and terrain (top checkboxes).
Also, sampling 2 sunlights is more costly to render.
If you'd like to do this properly and fast then use one lightsource, add a reflective shader to your surfaces and give the reflection tint the same tint you give it in that sunlight node.
Should your sunlight be yellow and you want less yellow reflections, then set reflection tint to the complementary colour of yellow. Then switch to HSB colour palette mode and play with saturation until you like what you see.

I'll report my finds on your cloud render settings later...

[Kexikus]

Thanks for the feedback.

The reason for the two sunlights is actually much simpler and way more stupid. It's a remnant from years ago when I had even less of an idea what I was doing. My goal was to reduce the glow in atmosphere so I duplicated my light, reduced the strength in both by half and disabled glow in atmosphere in one of them. At that point they still had the same color. That got changed only more recently. Why I disabled the specular highlights is beyond me though.

Either way, I now know that I can get that effect easier and cheaper by reducing the haze glow settings in the atmosphere node. So I will do just that.

Yes that filter.

I can't see any difference with that filter either.

[WAS]

More to the point of noise, increase Voxel Scattering Quality to 1000 - 1500 to remedy the issue in your scene.

[D.A. Bentley (SuddenPlanet)]

More to the point of noise, increase Voxel Scattering Quality to 1000 - 1500 to remedy the issue in your scene.

Increasing Voxel Scattering seems to resolve a lot of the noise in the darker areas in the clouds, but there was still noise in the lighter areas.  I did my test renders at 8k resolution with 1500 Voxel Scattering.
I was able to remove all of the noise by setting AA Sampling to 8, and customizing the noise threshold to .01, which is probably lower than you need to go but I wanted to be sure it would take away the noise.
It did take 7X longer to render though.  I typically just ignore this noise for working renders, and turn down the noise threshold for my final renders which sometimes take multiple days.
Of course if your doing animations this brute force method won't be of help.  Thanks for the TGD to test out.  I'll keep tweaking settings and see what else I can find.

[WAS]

You'd imagine increasing the render exponentially, you'd have to further compensate voxel scattering quality, as the previous settings are now covering a larger area. It fixes the issue on his file resolution. With a higher resolution you're effectively able to see the voxel areas clearer.

You pixel threshold makes sense at that resolution, similar to needing to keep stars stable in my skies at high resolution and needing a 0.01 pixel threshold with soft pixel reconstruction.

[D.A. Bentley (SuddenPlanet)]

Just another interesting finding.  Rendering your scene with the Robust adaptive sampler at AA16 was still noisier than when I did my Customize sampling at AA8 with threshold .01 and 1/64 first samples.
The AA16 Robust was actually much faster though to render.  Just out of curiosity I got the Robust adaptive sampler to use a Pixel noise threshold of .01 by putting samples to AA30.  Thats quite high! 

[WAS]

Just out of curiosity I got the Robust adaptive sampler to use a Pixel noise threshold of .01 by putting samples to AA30.  Thats quite high!

well that's not very "robust". lol

But can't you use both Robust Sampler and Customized AA? It doesn't switch to Legacy or anything.

[D.A. Bentley (SuddenPlanet)]

But can't you use both Robust Sampler and Customized AA? It doesn't switch to Legacy or anything.

My understanding is once you turn on "Customise sampling" the Robust adaptive sampler will allow you to change your noise threshold and first samples.  If you don't have "Customise" selected/ON, then the settings below are automatically chosen for you.  Leave "Customise" OFF and change the AA setting and watch the threshold change.  First samples defaults to 1/64 at AA4 and above, 1/16 at AA3-AA2, and 1/4 at AA1 and below.

Thats why I was saying if you turn AA up to 30 you should see the threshold go down to .01 (in Terragen 4.4.67 that is).

Love the Adaptive/Robust Sampler!  I can't wait for the day it can divide buckets and be even more adaptive as threads are freed up. 

[WAS]

I was just commenting cause you kept mentioning robust like it was different. Customized robust is still robust, just forcing the pixel threshold value.

But, also, like I mentioned, it doesn't seem very robust by definition having to go to such extreme levels, for a "robust" (strong) result. In fact the way you describe the setting stepping, and result, it seems more  delicate with the scene.

[Kexikus]

Thanks for the suggestions!

I tried both of them as well as a few combinations and arrived at a satisfactory result.

Voxel scattering at 1700 with AA10 left some noise in the brighter areas as D.A. Bently said.
AA8 with a pixel threshold of 0.015 with voxel scattering at 100 gave great results but was about 50% slower, so I searched for a combination and found it at a pixel threshold of 0.02 with voxel scattering at 1700. The result is very close to the lower pixel threshold but renders quite a bit faster.

I did not expect that I would need such extreme values for a relatively simple scene like this, but now I know better. Thanks again for the help everyone!