Metal Material Settings for Vray Advanced for 3DS Max (not Vray Next)

[Robert1977]

Dear users, dear Chaosgroup team,

I found these good pages for Vray next, describing the material settings for metals, in correspondance with the new metalness parameter.

https://docs.chaosgroup.com/display/...al+Shaders+IOR
https://www.chaosgroup.com/blog/understanding-metalness

Do you have a similar page for the good "old-school" VrayMaterial in Vray Advanced? We still use it, and I would need this information for some validation.
I have read years ago a post about these settings:

For Aluminium, steel, chrome etc, use a fresnel ior of 20-40, and a reflection color of almost pure white (RGB 255 255 255). For Gold, this reflection color is yellowish. The diffuse color is black.

Can you find this post for me or link to a page describing it?

Thank you much in advance

Robert Reimann

[seandunderdale]

In Vray 3.6 I never use a fresnel for anything over 8.0. That's the max I'll use for something like chrome, and it seems to match the photo car reference I get sent. Any other metals and materials are all less reflective than chrome (on a car anyway) so I use lower fresnels for everything else.

[Robert1977]

Thank you for your answer, but do you also use a reflection color of nearly white (RGB 220 220 220) then?
I have also had found tutorials with fresnel iors of 20.0 for steel and aluminum, since its frontal reflection seems not so much less than the reflection on the side. But as far as I understood, the fresnel ior is in vray 3.x only an approximation of metals, since fresnel ior (not refractive index) is for dielectric materials, not for metals.

[seandunderdale]

Yeh Ill pretty much leave the reflection colour at default. I might go 250 colour or 0.95 in the reflection amount, just to bring it away from being a full mirror, but honestly, if I render a comparison between a 255 white reflection and a 250, I cant tell the difference. I think people get bogged down in settings that actually have almost no visual impact overall. But My IOR of 8.0 is through years of rendering cars and I find it works. Other metals and shaders will be around 3 or 4 for steel and aluminium. Again, just from constantly using those type of materials and having to match to photos.

[Robert1977]

Found this interesting tutorial:

http://www.neilblevins.com/cg_educat...ome/chrome.htm

"The basic ingredients (for basic raytraced chrome) are as follows:

• No Diffuse
• Full Specular
• Fresnel Reflections
• IOR between 8 and 20"

This covers my experience with the material settings.

[seandunderdale]

I used to use higher fresnels, and sometimes map reflection value slots with ramps etc but that was back when HDRIs were shot badly. Now with well exposed HDRIs from a place like HDRHaven, there is enough intensity and contrast to use lower IORs (like 8, rather than 20) I find an IOR or 20 makes my materials look almost self illuminated compared to the materials around it like black gloss plastics and window glass. I agree with the other settings though. Ill also use some kind of imperfection map and assign a small blur value to everything. Its surprising how imperfect surfaces are once you get nice high res reference photography of them.

[Stefan_Laub]

the ior is not mainly the reflection intensity only but more the type of reflection Fresnel curve (which is a special curve for metals that resemble the real world values starting near 20 or more).

if not used metalness is used, ior for metals are very high 20 and more if used correct.(is approximation only)
the reflection color for non glazing angle is then not 255, to dim reflection to not shine too bright.

any of the "high ior setups" are only approximations though, as said.
the new metalness since NEXT is more correct in the way that it keeps the rgb 255 on the glanzing angles, but still has less intensity in the other view angles.
it produces more closely what you can see on pages like : https://refractiveindex.info
metalness workflow uses ior values only tiny bit over 1, both "systems" cant be mixed or direct compared.

[Ihno]

I don't think ior over 4 is realistic. https://forums.chaosgroup.com/forum/...43-maximum-ior
Better use the artist friendly complex fresnel osl, If it's an cpu render. https://forums.chaosgroup.com/forum/...ing-vrayosltex

[Stefan_Laub]

if you use metalness or complex ior then they are low as slight over 1 (using also a k value often)
if you not use that system, but classic vray ior, they are high - (note: as closest approximation) of 20 or higher.

so if you use normal ior without metal ness they are 20 or more to get that "metal like" curve
if you use metal ness the values are not higher than 2

[Robert1977]

Hi Stefan,

you mentioned the "non glazing (grazing) angle", do you mean the angle, where the normal has the same direction as the view direction (the front of a sphere looking at you), or do you mean the angle 90° away from the view angle (the sides of a sphere).
And what would be the reflection color like? Could you post here an example of how you would adjust an aluminium or steel material with the "old" approach (Fresnel IOR) and reflection color.

Thank you and kind regards

Robert

[dgruwier]

Here's how to manually do what Metalness does in Vray Next, using the same values given in the "Understanding metalness" blog post (which are also in the Vray documentation):

1. Set diffuse to black and disable fresnel entirely in the vraymtl.
2. Find the metal you want to use from the list and note the "Base (diffuse) color" and the IOR value.
3. Use a fresnel node with the given IOR value to blend between the given metal base color and a pure white color. Use that as the reflection color.
4. If you need to use a metalness map from a PBR material, use the vrayblend mtl with the metalness texture as the blend amount.

There's your very own deconstructed metalness shader. The result will be exactly identical, since it's the same as what VRay Next Metalness does, it blends the base and reflection colors using the IOR. Only major downside asside from having all the extra nodes floating around is that it doesn't work with glossy fresnel.

To validate if you did it correctly, add the material to a sphere in a scene with a 360 white dome light set to 1 intensity and render that. It should look exactly like the diffuse color in the documentation, but fading to white near the edges.

[Robert1977]

Here's how to manually do what Metalness does in Vray Next, using the same values given in the "Understanding metalness" blog post (which are also in the Vray documentation):

1. Set diffuse to black and disable fresnel entirely in the vraymtl.
2. Find the metal you want to use on list and note the "Base (diffuse) color" and the IOR value.
3. Use a fresnel node with the given IOR value to blend between the given metal base color and a pure white color. Use that as the fresnel color.
4. If you need to use a metalness map from a PBR material, use the vrayblend mtl with the metalness texture as the blend amount.

There's your very own deconstructed metalness shader. The result will be exactly identical, since it's the same as what VRay Next Metalness does, it blends the base and reflection (white) colors using the IOR. Only major downside asside from having all the extra nodes floating around is that it doesn't work with glossy fresnel.

Hi DGruwier,

what do you mean with "fresnel node" and use that as a fresnel color?
Are you in Max and Vray with 3.x? What is the node called exactly? Do you mean a falloff node? And I think you set the reflection color to rgb 255 255 255 in your approach?
Could you post a screenshot of your approach? Sounds really interesting.

Thank you
Robert

[piotrus3333]

metal shader in vray3 based on refractiveindex.info :

diffuse: zero
reflect: falloff map (see attached)
fresnel reflections: off

I have no access to my pc at the moment. this mat library is dug up from very old email - not sure what exactly is inside but output part of falloff maps (with rgb curves for different metals) should be correct:
https://we.tl/t-09dmQnpJO4

keep in mind that data from refractiveindex.info is based on samples of pure metals. alloys are much more common everywhere around but you will get the idea.

[Ihno]

And just another approach!

[dgruwier]

Robert1977 I'm in Maya so I just explained the general concept of blending the two colors using a node that outputs a fresnel as the mask (in Maya theres a vrayFresnel node). I think in 3Ds Max you can do it with the "Mix Map" node. You could also use the falloff node directly and just set the front color to the base metal color and switch the falloff type to fresnel, then change the ior. Use that as the reflection color in the vraymtl.
I'd say don't bother with manually copying curves off of refractiveIndex.org unless you're doing something scientific. The differences are so negligible it's not worth it IMO (it's a subtle effect to begin with). Spend that energy adding texture detail instead.

I also want to mention to anyone using complexFresnel, that it's really not very accurate. Here's a comparison Vlado made. The dashed lines are the accurate curves from refracticeindex.info, the solid lines are vray metalness (And by extension the method I mentioned above), and the dotted line is the complexFresnel shader.