anisotropic node

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The Anisotropic shader simulates a surface that has microscopic grooves, such as compact discs, some Christmas tree ornaments, brushed metal, or satiny cloth.

An isotropic material (such as Phong or Blinn) has the same specular properties in all directions. An anisotropic material has a distinguishable direction along which the surface is particularly shiny.

Aside from the attributes described here, the Anisotropic shader inherits many attributes from its parents Reflect and Lambert.

Other kinds of shaders you can use:

For unpolished surfaces, like chalk or matte paint, use a Lambert shader.
For metallic surfaces, such as brass or aluminum, use a Blinn shader.
For glossy plastic surfaces, bathroom mouldings, or polymers, use a PhongE shader.

In the table below, important attribute have their names indicated in bold in the description column.

Node name	Parents	Classification	MFn type	Compatible function sets
anisotropic	reflect	shader/surface:drawdb/shader/surface/anisotropic	kAnisotropy	kBase kNamedObject kDependencyNode kLambert kReflect kAnisotropy

Attributes (14)

angle, anisotropicReflectivity, fresnelRefractiveIndex, roughness, spreadX, spreadY, tangentUCamera, tangentUCameraX, tangentUCameraY, tangentUCameraZ, tangentVCamera, tangentVCameraX, tangentVCameraY, tangentVCameraZ

Long name (short name) Type Default Flags

anisotropicReflectivity (arfl) bool true

If Anisotropic Reflectivity is turned on, then the reflectivity of the material is calculated directly from its roughness.

If this attribute is turned off, the value in Reflectivity is used instead.

spreadX (sprx) float 13.0

Spread X controls how much the grooves spread out in the "X" direction. It ranges from 0.1 to 100. (The "X" direction is the surface U-direction, rotated counterclockwise by the Angle attribute)

When this value is increased, the surface appears smoother in that direction (that is, the specular highlight in that direction shrink). When the value is decreased, the highlight spreads out more in that direction, making the surface appear less smooth.

spreadY (spry) float 3.0

Spread Y controls how much the grooves spread out in the "Y" direction. It ranges from 0.1 to 100. (The Y direction is perpendicular to the "X" direction --- see the Spread X attribute above.)

fresnelRefractiveIndex (frfi) float 6.0

Fresnel Refractive Index affects the look of the anisotropic highlight. It does not affect the way light from other objects bends when when passing through the material, if the material is transparent and you are raytracing. As you increase the Fresnel Refractive Index, the highlight becomes brighter.

For transparent objects, you may want to set the Fresnel index to match the object's Refractive Index. This will give the most physically accurate result for the highlight.

angle (angl) float 0.0

Angle defines the "X" and "Y" directions on the surface relative to the surface intrinsic "U" and "V" directions. "X" is the "U" direction, rotated counter-clockwise by the Angle attribute. These "X" and "Y" directions are used by the shader to place the microgrooves that control the anisotropic properties of the shader.

This value ranges from 0 to 360 degrees.

roughness (roug) float 0.7

Roughness controls the overall roughness of the surface. It ranges from 0.01 to 1.0, with larger values giving a rougher appearance.

As this value is increased, the specular highlights are more spread out. This value will also affect the reflectivity of the material, if Anisotropic Reflectivity is turned on.

tangentUCamera (utan) float3

u-tangent at sample point

tangentUCameraX (utnx) float 1.0

u-tangent x value

tangentUCameraY (utny) float 1.0

u-tangent y value

tangentUCameraZ (utnz) float 1.0

u-tangent z value

tangentVCamera (vtan) float3

v-tangent at sample point

tangentVCameraX (vtnx) float 1.0

v-tangent x value

tangentVCameraY (vtny) float 1.0

v-tangent y value

tangentVCameraZ (vtnz) float 1.0

v-tangent z value