Vray 5.2 color material problems

[Karonte]

Good Morning. I have a problem with the new 5.2 upgrade. As you can see when I open my project in the new release( 5.2), the color of the rendered material is totally different. I opened only the file without touching anything. My old version was 5.1.

[caypiranha]

is it just this Mat.? others seem to be identical. Does it change then as soon you select another shader ball? if so, are all Materials becoming so "warm" then?
btw: who is who?

[Karonte]

I found this issue in this metallic material. this is the only that i clearly see different ( and the only one metallic without texture). the right one is from version 5.1 because, as you can see, the color of the material is similar to that of the diffuse.

[hermit.crab]

There is something the matter, however, it looks as if it's fixed in the latest internal nightlies. I'll test more and report back.

[Karonte]

There is something the matter, however, it looks as if it's fixed in the latest internal nightlies. I'll test more and report back.

I found that if i unlock the "fresnel IOR" the look will became similar. And i found that if i create a new material with same settings, the material is ok. I think there is a problem in load old scene materials.

[caypiranha]

Well done. But was it only in the Shaderballs, or has been represented in renderings as well?
I had a refresh problem in slate and when switching from Slate to legacy and back again, it was fixed.

[hermit.crab]

We had a discussion with the QA team about the matter and it seems the darker version is the physically correct one. There used to be an issue regarding a wrong "energy preservation" implementation in metals, which yielded a more vivid colour. I presume the shader was created at that time.

Otherwise, by unlocking the Fresnel value, the metal has returned to "normal" because of the default 1.6 Reflection IOR (the lock simply causes equal IOR values for refl. and refr.). Simply put, the dark result is caused by the high reflection IOR.

[Karonte]

so, s a RULE when i put METALLIC >0 i have to leave the default ior values, right?
So white reflection color + metallic. And the albedo ( diffuse) to drive the color of metallic. ( as pbr rules)

[hermit.crab]

so, s a RULE when i put METALLIC >0 i have to leave the default ior values, right?
So white reflection color + metallic. And the albedo ( diffuse) to drive the color of metallic. ( as pbr rules)

Not necessarily. The IOR values should depend on the specific metal you're after. Also, note that to be physically accurate, the metalness value should be either 0 or 1 (dielectric/metal). Check this article, there is a list of example shaders at the bottom.

[^Lele^]

On top of what's been already mentioned by Alex, the important bit is leaving reflection color to pure white when making a metallic shader.
And as you mention, use the diffuse color to drive the color of the metal itself.
In case of a differently colored specular, one should use the clearcoat (which is generally physically correct in principle.), so to ensure energy preservation (not always maintained when using a blend material in additive mode.).