issues with vray rt gpu and image based lighting

[kenzor]

I'm using win 10 with V-Ray 3.60.04 and 3dsmax 2018 and an nvidia gtx 1080

With a Vray Dome Light using an HDRI. This simple scene has very different results when using VRay GPU vs CPU or Adv.

GPU the ground is blue

CPU or Adv the ground is brown

It feels like the reflection amount is too big on the ground in the GPU render and washing out the diffuse colour.

Is this a bug? what can I do about this ?

Very happy to upload a version of this scene if someone can help

[vlado]

If you can provide a scene to support@chaosgroup.com it will be very helpful.

Best regards,
Vlado

[kenzor]

hi Vlado

I'm wetransfering a file to support

many thanks

[kenzor]

If you can provide a scene to support@chaosgroup.com it will be very helpful.

Best regards,
Vlado

Hi Vlado,

You should of received the wetransfer link via email. Let me know if got blocked for some reason.

Many thanks

ken

[Kristina.Georgieva]

Hello Ken,

There are two reasons for the difference between CPU and GPU:

1- Glossy Fresnel in the materials is on and it isn’t supported under RT GPU in V-Ray 3.60.04 (it is supported in V-Ray GPU Next).
2- There was a bug related to VRayNormalMap in GPU which was recently fixed (fixed in V-Ray Next).

When testing the scene with V-Ray Next, there is still small difference remaining. I have forwarded the scene to our developers, so they can advise if this is an acceptable difference (issue# VGPU-3267).

[kenzor]

Ok thanks for your feed back

Looking at the docs I can see now that Vray RT 3.6 GPU doesn't support : Glossy Fresnel, Translucency, Roughness or Dispersion.
and Vray Next gpu doesn't support : Translucency, Roughness or Dispersion.

Whats the correct setup for blurry reflections on the GPU in Vray RT 3.6 ?

[matanov]

Ok thanks for your feed back

Looking at the docs I can see now that Vray RT 3.6 GPU doesn't support : Glossy Fresnel, Translucency, Roughness or Dispersion.
and Vray Next gpu doesn't support : Translucency, Roughness or Dispersion.

Whats the correct setup for blurry reflections on the GPU in Vray RT 3.6 ?

Just use the reflection glossiness parameter in VRayMtl. "Glossy Fresnel" in V-Ray GPU Next is just an update to the way those kind of reflections are calculated (should appear more realistic).