Differences between Vantage and Vray CPU

[suzanne_doherty]

Hello,

I use Vantage for pre-vis, then switch to CPU for rendering.

However I'm seeing quite big differences between the two, mainly the reflections / specular (see the edge of the picture frame and wall as an example). Also see the floor for differences in the reflection glossiness.

Both are rendered with the same filmic tone mapping, although even without it this the differences are still there.

Any ideas?

[npg]

Shading graph for glossy/GI on? Any warnings in the log? It's hard to guess... If you share a (simplified) scene we could look for the cause.

Can you compare to V-Ray GPU as well?

[vladimir.nedev]

Can you send the scene to support for investigation ?

Might be something unsupported - light include/exclude for example or the bump map (where we don't match V-Ray exactly).

Greetings,
Vladimir Nedev

[suzanne_doherty]

I will email you Vladimir with the files

Also, here's the GPU version. Again slightly different, mainly with the bump maps, and of course the shadows as GPU doesn't support area shadows.

[suzanne_doherty]

Shading graph for glossy/GI on? Any warnings in the log? It's hard to guess... If you share a (simplified) scene we could look for the cause.

Can you compare to V-Ray GPU as well?

I should add that I'm using Live Link. Generally the only thing I change is I use Filmic Tone Mapping, with a White Point of 1. I don't tend to go deeper into the settings, and in this instance that's definitely the case.

[suzanne_doherty]

vladimir.nedev npg did you have chance to review the files I sent?

Cheers.

[vladimir.nedev]

vladimir.nedev npg did you have chance to review the files I sent?

Cheers.

What I have found so far

- the normal map on the black wall is working very differently in V-Ray for 3dsMax compared to V-Ray Standalone, V-Ray GPU and Vantage.
- the glass on the main window has receive/generate GI disabled, something that Vantage doesn't support.
- for this scene you need to set the GI bounces in Vantage to 4 to get as close as possible to V-Ray (we will consider increasing the max GI bounces).

The bump on the tiles doesn't match betwen Vantage, V-Ray GPU and V-Ray for 3dsMax.
All three render differently, but that's sort of expected - bump is very affected by the texture filtering and that's different in all three engines.

The normal map should in theory be very close, but there is some issue. I am still investigating it.

Greetings,
Vladimir Nedev

[vladimir.nedev]

Hello,

However I'm seeing quite big differences between the two, mainly the reflections / specular (see the edge of the picture frame and wall as an example). Also see the floor for differences in the reflection glossiness.

Any ideas?

The main cause of these issues is the "cast shadows" option for the window (Object001) being off.
Since it doesn't match the reflection visibility, V-Ray enters something called an "inconsistent specular visibility" mode for the ray and does additional clamping for the glossy reflections.
This is needed to prevent artifacts with the adaptive dome light and other adaptive lights.

Vantage doesn't do this, since it doesn't have the adaptive lights.
I am not sure we should implement it since it does this additional clamping.

The other, smaller part of the problem, is the normal map on the dark wall.
I will report it to the V-Ray for 3dsMax team.

Here is a comparison where "cast shadows" and "receive shadows" are ON for Object001.
I think the results are pretty close this way.

https://imgsli.com/MzY2MDkx/2/1

Greetings,
Vladimir Nedev