Overview

The Surface Tangent node has one purpose, to control the direction of anisotropic reflections when connected to an OpenPBR material. The OpenPBR material accepts a Surface Tangent in the Anisotropy Tangent ports for both Specular reflection and Coat reflections.

 

Example Graph

Connect a Surface Tangent to the Anisotropy Tangent in the Specular or Coat inputs of an OpenPBR material.

 

Tangent Source

Controls how the anisotropic direction is controlled from the following options:

• From Mesh: The anisotropic tangent is derived from the mesh.
• User Tangent: The anisotropic direction is derived from the User Tangent input.

Anisotropic reflections are stretched along the U axis of a mesh's UV unwrap when using "From Mesh" as the Tangent Source.

 

Mesh UV Channel

A UV channel can be specified here to control the direction of anisotropic reflections.

In the second example the UVs for the side of the pot are rotated 90 degrees so the anisotropic reflections stretch side to side instead of up and down.

 

User Tangent

A custom tangent can be specified to control the direction here.

 

Rotation

Rotates the anisotropic reflection. Input values range from 0 to 1 which is equal to the rotation angles 0° to 360°.

In the examples a texture is used to drive rotation on the bottom of the pot. Since the input values of 0 to 1 complete a full rotation, a radial ramp from black (0°) to white (360°) rotates the reflections all the way around the bottom of the pot creating the familiar anisotropic reflection effect. In the first set of examples the sides of the pot use a constant value to keep the reflections stretched consistently in the same direction up and down. However, in the second set of examples, a black and white noise is used on the sides which stretches the directions wildly in different directions — almost looking like a bump map.