LuxCoreRender Forums

So I'm testing Noise Threshold on windows with 2.6 but I noticed something weird, or I don't understand how it works or something is off.

I did some tests with noise threshold in one scene and I saw on the terminal how the "ToDo Pixels" amount was descending, I had a Samples Amount limit of 1024.
The noise threshold was configured at a high value on purpose, I had it to 150, and both the warmup and the test step samples to 16, I played with different values and I noticed no difference.

Then I went and disabled the Samples halt condition and I configured the Noise Threshold to 255, warmup and test to 16.

The render stopped at 1285 samples, shouldn't the noise threshold at 255 give me a super noise image, but near to instantaneous?

I mean, it's the biggest possible threshold, but I don't get a stop until sample 1285, and the result was as expected for that amount of samples.

Any ideas?

Are you using some kind of tile-like rendering with Sobol sampler ? Cache-friendly/Out-of-Memory settings ? Convergence threshold can work only with pure progressive rendering.

Can you post a test scene ?

Ah, that's the thing then.

I'm using Photon GI Cache, Sobol and Cache Friendly, it's the scene I sent you for the linux bug, you already have it .

I'll test without Cache Friendly and come back.

Mmmh, there was not difference, having it configured at 255 gave me 1760 samples, and it was slower than before (I assume that it was because I was using progressive and not Cache Friendly).

Shouldn't I get a super noisy image?

behavior also depends on Warmup & Test Step samples
I found 8 satisfactory

Yes, I get that, but shouldn’t it stop the render after the first test with a threshold of 255?

juangea wrote: Tue May 18, 2021 7:30 am Yes, I get that, but shouldn’t it stop the render after the first test with a threshold of 255?

While the input is presented in levels (0-255) it is not based on output RGB colour space (0-255) but rather, the scaled raw float light intensity 0-Inf.

Imagine that 0.0-1.0 is the same as levels 0-255. If your light has realistic brightness (e.g. an HDR or Sun lamp) then it might be as high as 60000.0, which would be approximately 15,300,000 RGB levels.

So if you have very bright lights and a lot of noise, it can take a long time to reduce noise down to the equivalent of even 255 above 0.

Then Noise Threshold is nearly useless in those situations?

juangea wrote: Tue May 18, 2021 4:06 pm Then Noise Threshold is nearly useless in those situations?

You might need to adapt it to your scene and use a higher value.

If you watch the console output while it's rendering, it will tell you the current noise value. When you reach the desired (visual) noise level, that is your threshold.
E.g. if I was happy with the noise level when it printed this message, I would use the threshold 306.823

For reference, this is my scene with an HDR with halt condition at noise threshold 255:

The thing is that in Blender we cannot put more than 255 I think.

@Theverat should know better I imagine.

P.S.: Yep, I just confirmed, in Blender the maximum value is 255, we cannot configure higher values.

P.S.2.: To Theverat (BYOB) I just changed the maximum limit of Noise Threshold from "max" to "soft_max" to allow freedom in maxmium written value, may be a thing to consider so the gates are open for custom values, what do you think?