Render (on GPU) doesn't look the same like the CPU

[dan_plattner]

Hi all!
I'm sharing 2 images of the same frame.
The frist one, was rendered on the CPU and it look like I want.
The second one was render on the GPU and the coffee beans looks completely different! (Bump, Reflection and Gloss)

I didn't change anything, just swich from Vray CPU to Vray GPU?
What can be the problem and how can I fix it?

UPDATE: I noticed that the LC calculation look nice and when it start th BF than the render start to look bad...

Thanks for the help!
Dan

[Morbid Angel]

Its because LC is calculated on cpu. I suspect the image that drives the glossiness is not supported by the gpu some how, or the color correction or something like that.

[dan_plattner]

Its because LC is calculated on cpu. I suspect the image that drives the glossiness is not supported by the gpu some how, or the color correction or something like that.

The glossiness is just a .jpg file and the CC is the CC of max...

[Morbid Angel]

right, if you try to isolate the issue. Like have a simple material with no textures and see if you get glossy reflection with just adjusting the shader, if you do, then plugin your map into it. If that breaks try to isolate why? it looks like a bug to me tho.

[vlado]

It would best to take a look at the scene; this case should be working fine.

Best regards,
Vlado

[matanov]

Please send me the scene - it will be way faster than guessing

[dan_plattner]

download link: https://we.tl/t-wkE3Tv2yl6

[matanov]

So I really have to start with this - V-Ray and V-Ray GPU are two different rendering engines. They don't have to render the same.

And now for your particular case - as far as I can see, there are three main reasons you are getting different shading :

1. You are using Diffuse Roughness which is not supported in V-Ray GPU (you can see that it's greyed-out in the UI)
2. The "Blur" function of Bitmap and VRayHDRI is calculating the effect in a different way in V-Ray GPU (and in V-Ray Standalone)
3. The "inverse gamma" of 0.45 in the bitmaps needs more than 8-bits in some cases. If you set your Texture Mode in Render Setup to Half or Float, it should be ok.

[super gnu]

i would also add, that in my experience a completely different bump multiplier is needed on gpu... (iirc i had to drop the bump from 5 to 0.3 to get similar result, or vice versa..)

[dan_plattner]

So I really have to start with this - V-Ray and V-Ray GPU are two different rendering engines. They don't have to render the same.

And now for your particular case - as far as I can see, there are three main reasons you are getting different shading :

1. You are using Diffuse Roughness which is not supported in V-Ray GPU (you can see that it's greyed-out in the UI)
2. The "Blur" function of Bitmap and VRayHDRI is calculating the effect in a different way in V-Ray GPU (and in V-Ray Standalone)
3. The "inverse gamma" of 0.45 in the bitmaps needs more than 8-bits in some cases. If you set your Texture Mode in Render Setup to Half or Float, it should be ok.

Thank you,
this is very helpful info. Next time I set up the scene in V-ray GPU from the beginning to avoid surprise as possible ^_^

[Karol.Osinski]

Hey guys, I have a similar problem with glossiness on GPU but using LayeredShader...