Vray scene material looks different

[BeneZ]

Hello,
I have a reflective material, and when I import this into Unreal - no matter which way (datasmith or vray scene) it looks very different.
I did a test with importing it as vray scene, screenshots at this link: https://wck.me/13Vv

When I did the same with a very simple chrome ball with a simple material without any usage of textures, it worked properly.

So I wonder what could cause this incompatibility.

[Alexander.Atanasov]

Hi BeneZ,

You are using a texture for the IOR value which I think causes the difference. Can you please try without that IOR texture or with a different one to see if it makes any difference?

Best regards,
Alexander

[BeneZ]

Thanks Alexander.Atanasov , good hint, I just looked in 3dsMax and there is indeed something strange with IOR.

I have two more questions here:
It lookes like UE is correct, but 3dsMax is wrong:
- the IOR is only a black map (which it shouldn't be of course, it just came like this once from Substance), but Vray renders in 3ds Max as if the fresnell reflection was deactivated (which is the same like IOR set on maximum, I guess)
Is there an explanation, why it looks so different in 3dsMax?

- metallness is set to zero, but this does not make any difference, neither in 3dsmax nor in UE. I wonder why this attribute hasn't any effect. (Actually metallness should be of course on 1)

I have put new screenshots into the same folder link https://wck.me/13Vv
(there on the UVmap this ring is only covering a small area on the top, so don't wonder why all the maps seem to be black at first glance)

[BeneZ]

Alexander.Atanasov
I tested a bit more just in 3ds Max:
IOR = 1 is completely black reflectivity,
IOR = 0 is same like unlimited full reflectivity without any fresnell effect. Is that right?

This would mean, that 3dsMax is correctly interpreting the black IOR, but indeed Unreal Engine does it not.

So I have a basic question:
- I wonder a bit about this IOR-map. It has values from 0 to 1 only in 16bit.
Is the space from 0 (full reflection) to 1 the same result, only mirrored, like values from1 to eternity (full reflection)?

- In case Unreal Engine can not handle IOR maps, is there a workaround? Often an asset has mixed material types (dielectric and metall) on just one UV space.

Many thanks

[Alexander.Atanasov]

Hi BeneZ

metallness is set to zero, but this does not make any difference, neither in 3dsmax nor in UE. I wonder why this attribute hasn't any effect. (Actually metallness should be of course on 1)

Metalness in Max typically works when Metalness=1, Reflection=white and you control the colour with the diffuse input. Fresnel IOR will not have any effect on the reflections in this case.

Is the space from 0 (full reflection) to 1 the same result, only mirrored, like values from1 to eternity (full reflection)?

Yes, you are correct. 0 to 1 and 1 to 100 are mirrored in values so I expect the IOR map to work correctly. Can you please attach the material setup(a simple scene would suffice) and the textures in the dropbox so I can investigate the problem?

Best regards,
Alexander

[BeneZ]

Alexander.Atanasov I have uploaded the zipped file, in case you want to have a look.
It currently seems to work.
Only strange thing at import is, that material is not automatically assigned.
Thanks

[Alexander.Atanasov]

Hi Benez,

I think I found what the issue is with the difference. The glossiness texture in Max is set to override gamma = 1.0



If you set it to Automatic then the result in Max and UE will almost match.

Try it and tell me how it goes.

Best regards,
Alexander