V-ray Interactive lighting vs actual render not the same

[jordyn_dane]

Okay...So i've been using Vray since Vray 3... I was extremely comfortable with it, I had just updated it to Vray 5 and i've been having non stop issues with lighting and the outside environment lighting (the sun...sky whatever)

I'm working on a project for work when I use the interactive render mode it shows the lighting perfectly, but when I got to produce the final render it's cold...and blue undertones (..aka cold.) i've never had this issue before I updated, Vray 3 always produced final renders exactly how the interactive mode shows... please help

i have both images attached, I took a screen shot of both and before anyone asks yes i did let an actual render finish all the way through and it still stayed blue/cool tone

[jordyn_dane]

bump bc help

[nikoleta.garkova]

Hey jordyn_dane,

Can you check if the Exposure Value (EV) option is set to Auto? If so, keep in mind that auto exposure works only with Production rendering. Try disabling it to see if that changes anything - see the attached screenshot:


If not, can you please send us the project so we can have a look and troubleshoot? You can forward it via our contact form, just make sure to mention this thread (or my name) in the email. Thanks!

[andy_smith]

Interestingly, I’ve just come here to post the exact same problem so I wonder if this is a bug or just that the OP and I are both coincidentally making the same mistake.

I’ll happily open a new thread but will add this here for now.

For me, I don’t believe it’s related to camera settings: I’ve always understood that the point of interactive render is to allow you to check all of your lighting settings, materials, frame buffer corrections, etc., without the time overhead of a full quality render. This means that the interactive render should, I believe, look identical to the production render?

I am seeing similar outcomes to the OP including a much colder white balance in the production render compared to the warmer white balance of the interactive render that I am aiming for.

To be clear, all I am doing to see the very different results is that I do an interactive render which I am happy with (geometry, materials, proxies, lights, frame buffer corrections, etc.) and then I end the interactive render and hit the production render button.

I can share the project (if you can tell me how to package it up) or screenshots.

Thanks,
Andy

[andy_smith]

OP, can you check something for me - I think I’ve figured it out. Is the word “Auto” blue next to your White Balance setting in the Camera rollout? Mine was and I’ve just found that if you set it to manual WB (ie the word Auto should be grey), then production mode has the same tone/white balance as Interactive mode does on auto WB.

if this works for you, please let me know. Perhaps someone from CG can explain why Auto WB is greyed out on Interactive mode but then gives cold tones on Production mode? Is it that our Interactive mode renders were ignoring the auto WB (if so - where were they getting their WB settings from?) and then when we rendered in production mode, the Auto WB just doesn’t work very well?

I’m using Brute Force and Light Cache in my Primary and Secondary engines in GI.

[andy_smith]

Further to the above, here are some test renders. It's confusing but it seems to me to be caused by using Light Cache as the secondary GI engine AND using auto White Balance. Change either of those and the problem seems to go away.



Production. GPU. BF/LC. AWB


Production. GPU. BF/None. MWB


Production. GPU. BF/LC. MWB


Production. CPU. BF/BF. MWB

[nikoleta.garkova]

Hi andy_smith,

As mentioned above, the Auto option will only work on Production rendering, so if enabled, switching back to Interactive will result in a difference. That being said, it is also worth to note that Light Cache should be selected as a secondary GI engine, so everything from your tests seems correct (BF/BF, BF/none won't allow AWB to be enabled).

This info is also available in our docs as well as by hovering on the Auto options in EV/White Balance camera settings.

If that's not the case and there are still some doubts, do forward a project which we could troubleshoot. Thanks!

[konstantin_chaos]

Hi andy_smith,

Everything that Nikoleta wrote is correct.
I just want to give you some additional info regarding your observations.

The Auto White Balance as well as the Auto EV both require the Light Cache GI prepass to function.
This leads to the following:
- The Auto options do not work in interactive since Light Cache is automatically replaced by the Brute Force method
- The Auto options do not work when you change the secondary GI engine

And here's the reason why Light Cache is required:
To adjust the EV or WB V-Ray needs to start rendering the image, sample enough color values.
When you render without a prepass (without the Light Cache) V-Ray starts sampling and later can determine the required adjustments.
Unfortunately if we want to adjust the EV at this stage we have to throw away the samples already taken and reset the process.
This is obviously sub-optimal and led us to the decision to calculate the Automatic adjustments only when the Light Cache prepass is enabled.
This allows for the Auto values to be determined during the prepass keeping the final render time (the final image sampling) unaffected.

We could have also adjusted the exposure and white balance as a post-effect (not baking them in the image) but this leads to other complications.
It would have led to sampling issues when you try to use the automatic exposure to brighten up an extremely dark image (V-Ray samples less in dark areas to optimize performance).

We have future plans to remove this limitation by enabling Light Cache during interactive rendering.

Hope that clarifies things to some extent,
Konstantin