Help creating a brushed metal material with anisotropy

[kimmo_hernborg]

Hi

I need help creating a brushed metal material with anisotropy.

1. With the material with metalness enabled, the roughness channel is where I put a map to simulate the brushed surface right? (The reflection color/texture doesn’t seem to do much, it seem to be either on or off.)
The anisotropy is supposed to stretch the reflections in direction perpendicular to the brushed texture. In 3ds max with an older version of Vray I had an UW box map applied to all objects with a brushed material. The UW map was rotated to have the brushed texture appear correct on the objects. The anisotropy rotation value was adjusted to make the anisotropy stretch perpendicular to the brushed texture.

When I import one of these objects I get weird artifacts when I apply anisotropy and use the specified Uvw generator. Almost like there are intersecting polygons or something.

2. I´m obviously missing something, can someone help me?

3. Setting the anisotropy to a negative value seem to have the same effect as having it at positive value and adding rotation? (Ani 0.6 rot 0.25 seem very much like rot -0.6 rot 0.0) Is there any difference, and is there any reason to use one over the other?

Best regards

[sirio76]

Hi, on our product page we have a free shader pack with some anisotropic metals, you can download it (sample shaders) and see how I build them: https://www.3dtutorialandbeyond.com/...ders-cinema4d/

[greymiura]

Hey Kimmo,

hope you found a solution in the meantime?! I experienced some similar issues with the Specified Uvw Generater option activated under v5.10.22. They dissappeared after updating to .23, so make sure to use the latest version.

Here are some additional thoughts.

1. A texture map with the usual brush strokes is supposed to be used in the glossiness / roughness slot, that's correct. Only with a very rough surface it may be reasonable to use an additional map to control the strength of the reflections in the cavities, where some light may get trapped, but as you use metalness, this map has to be in the diffuse color slot (with metalness on, the specular color defines the effect only at the glancing angles where the cavities become negligible). These maps have absolutely no influence on the anisotropic distortion or direction (besides the fact that the anisotropic effect gets more obvious the rougher the surface is).

2. Make sure to use a proper uv layout, but as you mentioned that the stroke direction seems to be correct, that shouldn't be the problem. I'm not sure if a non uniform or very extreme u/v ratio can cause any problems.

3. And as you mentioned a positive anisotropy value makes the effect perpendicular to the one with the corresponding negative value and a 0.25 rotation value causes a 90 degree rotation as well. These are just values and there's no difference between 0.6 anisotropy with no rotation (or a 0.5 rotation) and -0.6 anisotropy with a 0.25 or 0.75 rotation. Both become necessary when working with maps to control both the strength and the rotation at a given point of the uv map.

At least that's how I understood these things... Good luck!

[kimmo_hernborg]

Hey Kimmo,

hope you found a solution in the meantime?! I experienced some similar issues with the Specified Uvw Generater option activated under v5.10.22. They dissappeared after updating to .23, so make sure to use the latest version.

Here are some additional thoughts.

1. A texture map with the usual brush strokes is supposed to be used in the glossiness / roughness slot, that's correct. Only with a very rough surface it may be reasonable to use an additional map to control the strength of the reflections in the cavities, where some light may get trapped, but as you use metalness, this map has to be in the diffuse color slot (with metalness on, the specular color defines the effect only at the glancing angles where the cavities become negligible). These maps have absolutely no influence on the anisotropic distortion or direction (besides the fact that the anisotropic effect gets more obvious the rougher the surface is).

2. Make sure to use a proper uv layout, but as you mentioned that the stroke direction seems to be correct, that shouldn't be the problem. I'm not sure if a non uniform or very extreme u/v ratio can cause any problems.

3. And as you mentioned a positive anisotropy value makes the effect perpendicular to the one with the corresponding negative value and a 0.25 rotation value causes a 90 degree rotation as well. These are just values and there's no difference between 0.6 anisotropy with no rotation (or a 0.5 rotation) and -0.6 anisotropy with a 0.25 or 0.75 rotation. Both become necessary when working with maps to control both the strength and the rotation at a given point of the uv map.

At least that's how I understood these things... Good luck!

Thanks for your help. My issues seem to have been resolved after using the latest version of Vray.

I´m using a large noise map in the bump channel to simulate the surface not being completely flat. In the older version av Vray that lead to some strange artifacts when using anisotropi, that seem to have been resolved in the latest version as well.