CPU vs GPU glass rendering - HUGE DIFFERENCE !!!!

[remi11]

I'm new at Vray and just bought my first GPU cause my cpu got to 100Celsius when rendering.
Can someone please tell me what settings do i need to change in Asset editor in order to make the glass with GPU rendering transparent and similar to the cpu render ?

[andybot_cg]

If you're starting with an old vfs2 material, this is expected because the GPU render doesn't convert the reflection layer like the CPU render does. I suggest making a new material starting with the Vray presets.

[remi11]

i did try with the preset glass in vray but that also is opaque, exactly what settings should i change ?

[Peter.Chaushev]

Hello, Remi,

There shouldn't be any difference between rendering glass in CPU or CUDA in the latest V-Ray 3.40.04 build.
Could you please make sure you're using that version?
If you are still having trouble, please send over the scene for investigation either here in the forum thread, through a private message, or in an email addressed to support@chaosgroup.com (accompanied by short description).

Kind regards,
Peter

[andybot_cg]

i did try with the preset glass in vray but that also is opaque, exactly what settings should i change ?

Maybe check if the back face is also the glass material?

[remi11]

Thank you Andy and Peter , i did install V-Ray 3.40.04, and both faces are glass but i get the exact same result.
I attached the .skp and .vropt
Peter i really hope the problem is on my end cause there really shouldnt be any difference between the CPU and GPU renderings

[remi11]

Can someone please fix this bug caused i bough a one month licence and without this feature i can not work.
With CPU rendering a long video output my procesor gets to 100C and the whole thing shuts down so i really need GPU acceleration

[andybot_cg]

the GPU render doesn't convert the reflection layer like the CPU render does. I suggest making a new material starting with the Vray presets.

Like I said in my first quote - you have a "reflection" layer in your glass material. Sorry if it was confusing because I assumed you used an old vfs2 material. GPU engine does not render that layer as expected and makes the mirrored reflection like you see. I've made a glass material for vfs3 a while back that works in both. Hope this helps. You can increase the Fresnel IOR of the material if you need a stronger reflection.

Andy

[Peter.Chaushev]

Hello, Remi,
Andybot already pinpointed the issues with your material. Additionally, the Sky texture is not supposed to be placed in the map slots you've used.

It appears the windows you've created constitute of just a single face and have no thickness. In such cases you might want to use the glass presets from the Diagrammatic library category (although they do not produce physically-accurate results).
If you'd like to use any of the regular glass presets, first I suggest adding some volume to your windows and then decreasing the Refraction > Fog multiplier value.

Contrary to what I stated in my previous reply, there is actually one difference between CPU and GPU rendering of refractive materials - the fog color multiplier is not being taken into account in CUDA mode. This should be amended in one of the next feature updates.

Kind regards,
Peter

[remi11]

Thank you very much Andy and Peter it finally works ! Sorry i'm really new at this