Strange reflection behaviors with new version of V-Ray

[joaovictor_rangel]

Hello! My materials have been exhibiting strange behaviors since update 6, mainly regarding glossy reflections: often the material shows no reflection at all, even though I have configured it correctly.
I have already tried a clean uninstall of both SketchUp and V-Ray, but the problem persisted. Below, I will send two scenes for you to see the difference, the first one rendered with V-Ray 5 and the other with the latest version:

V-RAY 5

V-RAY 6


See how materials with reflections behave differently, especially the black metal.
Here is its configuration.

[konstantin_chaos]

Hi joaovictor_rangel,

I was not able to reproduce the discrepancy you've shown.
Is it possible for you to share a simplified version of your project for us to test?

Thank you in advance,
Konstantin

[joaovictor_rangel]

Hi joaovictor_rangel,

I was not able to reproduce the discrepancy you've shown.
Is it possible for you to share a simplified version of your project for us to test?

Thank you in advance,
Konstantin

Sure!
Here's the link to the file:
https://www.dropbox.com/scl/fi/d5rxo...=a2bwzwzm&dl=0

[joaovictor_rangel]

I’ve identified that it’s some bug related to the fresnel of the reflection layer. When activated, the reflection doesn’t behave as it should; when deactivated and settings are changed, it shows reflection (the mirror has fresnel disabled, for example).

[konstantin_chaos]

Thank you for sharing the model.
However, I need the original file, the one saved with V-Ray 5 in order to see what is changing from version to version.

[joaovictor_rangel]

The bug has been identified
So, I reviewed the parameters of all materials in scenes and found an unusual option activated in some.
It was marked like this in the opacity layer, so I reset this setting, and the entire scene returned to normal now.


This is creating some kind of weird volumetric bug in the model, deactivating the fresnel of reflections.
Many materials of the scene are with this option, but in V-Ray 5 worked fine

[konstantin_chaos]

Hi,

Thanks for the update.
However, changing the Opacity options doesn't seem to make any difference for me (I tested with the S7 - Metal branco Fosco1 material).
Can you post a bit more information about this?
Sharing the project saved in V-Ray 5 would also help.

Konstantin

[joaovictor_rangel]

Hi,

Thanks for the update.
However, changing the Opacity options doesn't seem to make any difference for me (I tested with the S7 - Metal branco Fosco1 material).
Can you post a bit more information about this?
Sharing the project saved in V-Ray 5 would also help.

Konstantin

We kind of have to decipher which material is problematic by unchecking this option in all the ones that are activated. In this case, unchecking the "Diffuse Texture Alpha" box of the "S7 - FORRO BRANCO" material solves the issues in this file.
Note that even without any active opacity settings, the material has a blue arrow, indicating that something is activated. When I uncheck the "Diffuse Texture Alpha," the entire scene returns to normal.


I don't have this scene in the previous version of V-Ray anymore; the save overwrote the file. I only have the images generated previously.

[konstantin_chaos]

OK, now I see what's going on.
The real reason for the difference is the Dirt texture connected to the diffuse slot of S7 - FORRO BRANCO
When it's used as a opacity source, it makes the surface appear dimmer in reflections which is a bug in my opinion.
The entire scene changes just because most objects reflect the ceiling...
I'll log this for the V-Ray Core team to investigate.

Note that disabling the checkbox of the Diffuse slot will not resolve the issue because it is still going to act as an opacity source.
The best workaround is what you've done - disable the Opacity Source checkbox.

Thank you very much for taking the time to debug this!