# Change the direction of anisotropic?

I'm working on a brushed aluminum material on a flat surface. but without the anisotropic it doesn't look right. I want the light to bend but not the way it does by just adding anisotropic in the principal shader. That would give me a radial brushed effect like on a CD I want the reflections to be stretched like in this photo example as if the aluminum was brushed in one direction. Thankful for help.

## 1 Answer

Regardless of whether you use Principled BSDF or Anisotropic BSDF, the direction of anisotropy is set by the combination of the Tangent input and the Rotation field. The tangent is a world-space vector perpendicular to the normal, set most easily by a tangent node; the rotation rotates the given vector around the normal.

If you use a tangent node to input a radial tangent, you'll get a radial tangent, in the object-space plane specified. If you use a tangent node to input a UV tangent, you'll get the vector of increasing U for the UV map you specify.

You can even create an arbitrary, per-sample vector yourself, without using the tangent node. (Notably, you can make a radial by hand that's better than the built-in radial. But mostly nobody's going to take advantage of home-built tangents.)

If you don't specify a tangent, anisotropy defaults to a radial Z tangent.

• Oh, nice. That pesky tangent input Jun 14, 2021 at 16:46
• is the tangent node possible to use with the Principaled node?
– Rock
Jun 14, 2021 at 17:17
• @Rock Yes, it's exactly the same for a principled BSDF, except "rotation" is called "anisotropic rotation." Jun 14, 2021 at 17:24