GI of standard Vray Production is very different Active Shade RT CPU

[dsolod]

Hi!

We imported scene from the Sketchup, applied Vray Scene Converter and adjusted some of materials.

We are getting very strange results in rendering the image with standard settings in Active Shade Mode and then Production Mode (VRay was restarted)
Attached are the pictures of RawGI element for both renderings.

Switching from the Light cache to to the Brute Force solves the problem.
Also, override material kind of fixes the problem but we do not know how to find the issue.

Please advise

Thanks!

Dmitry

[yavor.rubenov]

Hello,

When running Active Shade we don't calculate the Light cache - so you get GI as if you are using BF/BF. In Active Shade only loading the Light cache from file is supported.

Best regards,
Yavor

[dsolod]

Hi Yavor,
Thanks for explanation

But we still would like to confirm that everything is correct in our settings.

Attached is a simple scene rendered twice with BF+BF and BF+LC
The only difference is changed RGB level for the bitmap. This is how we adjust the brightness of materials sometimes.

If in the second case the both renderings are so different but correct then we can not rely on Active shade mode to quickly adjust the scene or we need another way to adjust the material's appearance

Please check.

Dmitry

[yavor.rubenov]

Generally if you plan to use CPU rendering and the V-Ray Adv renderer - you can use the IPR for interactive scene adjustments. IPR will calculate Light cache if it set up so you will get the same results.

[dsolod]

Yes, I understand that and probably we will use IPR

But before that could you please confirm that there is nothing wrong with our settings and please explain why the GI and final renders look so different with the same settings

Thanks

Dmitry

[yavor.rubenov]

In your scene if I render with V-Ray Adv with BF/BF and change the number of BF bounces to a value higher than 3 I get results similar to the ones with Light cache. The light cache itself simulates a lot of light bounces and because of that with the default of 3 BF bounces there is a difference in GI.

Setting the RGB level of the bitmap to such high values makes the materials behave as if they were emitting light - is that what you need ?

[dsolod]

Your second statement about RGB level is very new for me!
I'll search it and make some tests about it.

Thank you very much for pointing this out!

[Art48]

See the texture as a multiplier of white. If you have a texture with a value of 0.5 somewhere, it will be a mid gray. 1.0 will be pure white. And if you increase the RGB level of your texture so far that some or many pixels with actually have a value brighter than 1 (or 255) you will still see these areas as pure white with your eye but for the renderer they are actually emitting light (the intensity being the difference of the actual value minus 1.0 in coarse terms)