(SOLVED) White specular dots when using bump or displacement

[loresuto]

Hi all,

I'm noticing an issue with bump and displacement maps in Octane for Blender. I seem to get very bright dots that can only be removed by turning Specular down to 0. The dots are most evident in the shadow terminator edge. (see attached image)

This might have to do with texture filtering, where the texture needs to be smoothed (for example bicubic filtering). Does Octane have texture filtering? Though, I'm not getting this issue with the same texture in Cycles, even with the texture filtering set to linear, so I'm not sure that's it.

Does anyone have any clues as to what I'm doing wrong?

Thanks for your help!

[kabakZ]

Hi,

Can you test the same scene using 2019 version? I'm not 100% sure, but it could be caused by the new AI lighting sampling implemented in 2020.
Also, as many people have reported, and I can confirm this personally, the noise info pass was changed in 2020, and it never eliminates noise or fireflies in out of focus areas.

You can also check the info passes to see what exactly is causing those white dots, a diffuse channel (texture filtering) or speculars.

[loresuto]

Hi KabakZ,

In looking at the preview passes, the line of dots on the shadow edge is in the diffuse pass, while the dots in the light are mainly in the reflection pass. (See attached)

The Octane denoiser on the beauty pass seems to clear up some of the issues, but there are still some white specks.

I'm using the default settings with the Kernel set to Path Trace. (You can see the settings in the image on the right).

Thanks

[linograndiotoy]

That's related to the way Octane Standalone works(so it's not a specific Octane for Blender issue but a moreo general one that can only be solved in the core).

[funk]

When you see these kinds of issues, it's usually because your bump map is way too strong.

I don't know the technical details, but a bump value of 1.0 seems to be an approximate "bump distance" of 1m(?).
So set the texture's power to something more reasonable (0.01 or 0.1). You can also do this by connecting a multiply node after the bump texture too.

Next thing I'd do is reduce kernel > GI clamp to 10.
You can often get away with values between 1 - 100, but be careful it doesn't start affecting your lighting (by making things darker).
You sacrifice some "realism" because it reduces caustics/bounces, but it can help remove very bright pixels/noise.

EDIT: I see blender defaults kernel > caustics blur to 0.000. Standalone defaults to 0.01. I would recommend setting it 0.01, to help reduce caustic noise too.

EDIT 2: I would also enable adaptive sampling. It allows Octane to concentrate on noisy areas, and stop wasting samples if the area is clean enough.

[kabakZ]

+1

The default GI clamp value is up to high and causes fireflies, try reducing it to 10.0 instead (recommended value). Caustics blur also helps.

[loresuto]

Thanks so much for all the tips! Exactly what I was hoping for.

The GI clamp value seemed to help the most. It's interesting that the Caustic blur default is different in standalone vs. Blender (It makes me wonder if other settings aren't quite the same?)

Funk, thanks for the tip about the Multiply Tex node - I was wondering how to attenuate a texture power's bump without affecting the Albedo, and that does the trick.

Octane is super fast with displacement, it almost seems as fast as the Bump! There's texturing filtering in the Texture Displacement node, but is there a way to add texture filtering to a Bump map in Octane? I think that would help in this case.

Do you know if there any Blender Octane example files available that show sample best practices for settings and texturing? It's really helpful to see how experienced users go about things.

Thanks again!

[funk]

No, there is currently no control over texture filtering.

[J.C]

Hi all,

I'm noticing an issue with bump and displacement maps in Octane for Blender. I seem to get very bright dots that can only be removed by turning Specular down to 0. The dots are most evident in the shadow terminator edge. (see attached image)

This might have to do with texture filtering, where the texture needs to be smoothed (for example bicubic filtering). Does Octane have texture filtering? Though, I'm not getting this issue with the same texture in Cycles, even with the texture filtering set to linear, so I'm not sure that's it.

Does anyone have any clues as to what I'm doing wrong?

What is your material roughness setting? Low values can cause this issue.

[loresuto]

Hi J.C,
The dots were present with even a medium (.5) roughness, though they were were a bit worse as roughness wasreduced. The issue, in this case, seemed to be the GI clamp. Setting it between 5-10 as has been recommended seems to deal with the issue for me.