Multipass compositing not working properly

[hardrock_ram]

I am having some problems compositing a multipass render the right way with Vray and Nuke.
Its been a couple of years since I did this the last time, and now I am having some problems in getting my multipass composite image to match the original rendered beatuy pass.

Here is a barebone Nuke composite. I don´t understand why I don´t get an exact copy of the beaty pass with this. It doesn´t make any difference whether refractions are included or not.
This is not my real composite, but since I can´t even get this to work, I figured I start here.






Here are all the render elements:





I use Vray Next 1.1, 3dsmax 2018 and Nuke 11.3

Appreciate any help

EDIT: I see that individual light passes added together does not equal the lighting pass. Why not? (The lights are rendered as diffuse type)
I get something much closer to the desired beauty pass if I add all the separate lights as a diffuse pass instead of the lighting pass, but its still not exact.

[maxedesa]

How different is the result? Your setup there usually works, but every now and then, its slightly brighter, and I'm not sure why. You may also need SSS and self illumination, but that's probably not the problem.

I prefer compositing using Light Select layers, which is excellent with the "full" mode. But "full" gets too complicated when you have self illuminated objects in the scene (being reflected).

[vlado]

Can you post a scene for this? There was a problem with the blend material, which should be fixed in the latest nightly builds and I want to check it out.

Best regards,
Vlado

[maxedesa]

I'll check into the last scene where this was happening. If it has blend, you want it sent to support@?

About compositing in full mode - If Self Illumination pass had an option for its own full mode, and maybe another pass for VRayLightMaterials, I think comping would work pretty simply. How does everyone else deal with comping light select channels?

[hardrock_ram]

For maxedesa and vlado:

As you can see in the image, there is a distinct difference:




The difference is mostly in areas where dirt and scratches are coming through. I use blend materials to achieve this.
Another strange thing is that the results are much closer if add each diffuse light_select element together instead of using the lighting pass. But there are still slight deviations in RGB values.

I sent a file with the material and render setup. The ticket number is 100-315-412-4 
Its a big hassle to send files larger than email size since I am on a locked down corporate network. See if you can make due with the file I sent you. If not, I will start arrangements to send the complete scene file .

A quick scene description for things that cannot be seen in the file:
-No plugins are used, and Vray and PHXFD are the only plugins installed.
-I use only Vray lights and Vray Materials. The camera is a Vray camera.

[hardrock_ram]

Vlado or maxedesa,
Are there any updates regarding this? You mentioned something regarding blend materials and how it might cause problems ...

-Erik

[Svetlozar Draganov]

Yes, please excuse me about the delay.
I sent you an email from our system, please check it.

[hardrock_ram]

Okay Svetlozar.
I will not se that email before monday, but I will reply then

[maxedesa]

Hello,
Did you ever find a solution for this?

[hardrock_ram]

No, sorry.
My employer has a big no-no on sending CAD and related material to third parties, so I never sent the file to Chaosgroup. I was to much of a hassle ...