Anisotropy in UV space?

[greymiura]

I give up. I really tried to figure this out on my own, but it doesn't work. And I could not find something about it in the forum or in the online manual either. So may I ask you for some help with this?

There is this

UV Vectors derivation

scroll down in the Anisotropy section of the V-Ray Material's reflection channel with a

Specified Uvw Generater

option. Does that mean that Vray is able to set the anisotropy direction according to the UV space? Which would be really great and exactly what I'm looking for. The manual says

Allows the user to assign a UVW Generator for the anisotropy effect

so I even tried to use this VRayUVWGenChannel shader in the materials for cosmos browser objects, but somewhere I read that that is only for compatibility reasons anyway.

So is it possible to use the UV space to define the direction of the anisotropy effect? And how does it work? Or am I getting this totally wrong?

[sirio76]

Do you have an example of what you are trying to achieve?

[aleksandar.kasabov]

Hello greymiura,

Setting the "UV Vectors Derivation" to "Specified UVW generator" will allow you to control the direction of the anisotropy effect by editing the UV map of the object.

[greymiura]

sirio, Aleksandar, thanks for your replies!

sirio, this is just a drastic example for what I'm trying to achieve: Imagine a metal tube with a brushed surface that is bent in multiple directions.

The object on the right is some kind of reference: It consists of separate geometries, eight cylinders and eight torus segments with their respective local coordinate systems and the anisotropy direction defined in local object space for each of them. The anisotropy effect looks like it's supposed to, doesn't it?

If I try to achieve the exact same effect, but with a single object (with a rectangular uv setup) and the "Specified Uvw Generator" option selected, the result is the same in certain parts of the object where the tube direction is parallel to the object's x axis and totally different where the tube direction is parallel to the y and z axis. What I expected to see was the effect of brush strokes in v direction / a specular distortion in u direction (or vice versa?). The second image just shows the uv setup of the single object and the separate parts of the compound on the right.

What I'm really looking for is this subtle anisotropic distortion that you see in certain fabrics and wood surfaces. And having this rendered on a complex plywood geometry for instance...

You can find the two objects with their materials here: https://we.tl/t-uMzyJbdiHw

Did I get the concept just plain wrong or is there a mistake in my setup?

[aleksandar.kasabov]

Hello greymiura,

I tested your scene and rendered the same result when using the "Specified UVW Generator" for the UV Vectors Derivation on the single object as the one "Local Object Axis" on the ObjectAssebled. You can check the following video where I test this. You can see that there is no difference in the anisotropy effect on both objects.

[greymiura]

Hello Aleksandar,

thank you so much for your efforts! I just couldn't believe it at first and tried once again - and it rendered perfect. ???

Then I remembered that I used V-Ray 5.10.22 for the renderings above and had updated in the meantime. So I went back to .22 and got the wrong result again.

It wasn't mentioned in the release notes, but obviously the issue dissappeared with the latest update... Which is great news, anyway.

Thanks again and have a nice day!

[aleksandar.kasabov]

Hello greymiura,

I am glad to hear that using the latest update fixed this issue for you. Should you have any queries in the future, don't hesitate to let us know here on the forum or open a support ticket via our contact form. Cheers.