Black dots or pixels on render ...

[rmara]

Hi there Octane pro's

i'm preparing a 3D teaser rendered in Octane for one of my comics "the three ghosts of Tesla"
and i'm having some problem with rendering settings...

I tried with Octane 3.08 and Octane 4 and got the same result

On some scene with several lights, I have black dots remaining on the image
even with 36000 samples

the higher I go the less noise I have but still getting those black dots at 36000 samples, really !

Here is what I mean ....
The s scene here rendered at 2000 with only one light and one hdri
and without the "Tesla" item, the new octane 4 denoiser just works fine and give me a great sharp image even at 500 samples

The attachment Travis desk piqué .jpg is no longer available

And the same scene with the "tesla"item which as some geometry on which an emission material is set...
at 36000 samples

You can see the difference ...
And here are the rendering settings

Anyone has suggestions on how to remove those black pixels or dots ?

[milanm]

Judging by the max samples number I'm guessing you are using adaptive sampling? If you are, lowering 'Path Term.' parameter close to zero or adjusting 'Expected exposure' setting could fix that. That could happen in dark or underexposed scenes just like that one.

Cheers
Milan

[rmara]

Thanks for answering so quick Milan. And also thanks for the detailed advice, I'll inquire on these settings on a new rendering and see how it goes !

[rmara]

Unfortunately this adjustment didn't work.
I still have the black dots and now the rendering of the image at 18000 samples which was taking 1H20min before is taking about two hours, almost as long as the 36000 samples rendering ... Not really what I was looking for...

May be should I shut off the adaptiv sampling for this scene ?

It's damn frustrating considering I need that "Tesla ball" item in the scene and the scene renders just fine with this extra light coming from it ...

Another thought ? Would be a great help...

[milanm]

You could try changing group pixels to 'None' and noise treshold a bit lower. I'm 100% sure that this can be fixed by adjusting the adaptive sampling settings but because it's such a long render you could also try locking (padlock) and lowering the resolution in the LV by changing the scale value (the number next to Chn:) to 0.5 or 0.25 and monitoring how noise pass looks like. And then experiment with different Expected Exposure and Noise treshold settings, even really extreme ones. Then, once you're sure that adaptive sampling is not masking the area on the desk with the dots too early and it looks clean in low res you could switch back to full to see if it improves anything. Of course, disabling Adaptive would be a last resort measure I guess. Also, I have to say, rendertime is unusually high for a simple scene like that so there must be a way to optimize it more. How did denoiser do in V4? Also in V4, because that lamp is a small light source, you could try to enable AI Light and see if that cleans the image a bit faster or maybe even scale that light a bit up.

Cheers
Milan

[pxlntwrk]

I Rmara,

i had this black dot s "issue" in a recent project.
try to increase the "min samples" in adaptive sampling tab (1024 pe) and the group pixels to "none".
Try to increase the sampling rate in the light settings.

or dont use adaptative sampling who I believe is the cause of these black spots...


Keep us in touch

cheers
Cedric

ps/ if you want/can PM me the scene, i will take a look