Anisotropy Vector Field Icon

asAnisotropyVectorField

A node that manipulates anisotropy vector maps and outputs a anisotropy vector for use in BxDFs that support anisotropy.


Parameters

Field Parameters

Field Color
The anisotropy vector map color.
Rotation Angle
A rotation angle, in degrees, from -360 to 360 degrees, to rotate the input anisotropy vector map. This is an absolute value to re-orient the initial anisotropy vector map, non-texturable.
Field Mode

The input anisotropy vector map can have the anisotropy directions along X and Y, encoded in the Red and Green channels, or in the Red and Blue channels. Typically, RG encoding is used in applications such as RenderMan [1], while RB encoding is used in applications such as Modo [2] or Softimage [3]. The values allowed are therefore

  • Red/Green as XY
  • Red/Blue as XY

Rotation Parameters

Rotation Value
This parameter rotates the RG or RB vector field, and unlike the Rotation Angle parameter, this parameter takes as inputs values between 0.0 and 1.0, and is texturable. Internally this is mapped to [0,360] degrees.
Rotation Mode

The rotation computed earlier in Rotation Value can be added to the vector field, or the rotation can be applied to both directions along a central axis. That is, the rotation can be mapped from the input [0,1] values to [0,360] degrees (Absolute), or to [-360,360] degrees (Centered) - where a value of 0.5 means no rotation. Values below 0.5 means counter-clockwise rotation, and values above 0.5 imply clockwise rotation. The allowed modes are therefore

  • Centered
  • Absolute

Output Parameters

Normalize Output
Parameter that forces a normalization of the final anisotropy vector. The default is to enable it.

Surface Normal

Surface Normal
The world space, unit length shading normal, bump mapped. Not a tangent space nor a object space normal.

Outputs

Anisotropy Vector
The final re-oriented, RG or RB encoded anisotropy vector.

Footnotes

[1]See RenderMan’s tangent field for details on PRman’s implementation.
[2]See Modo anisotropy help for details on the Modo implementation. Unlike PRman’s, the XY data is encoded in R and B channels, not R and G.
[3]See Softimage anisotropy patterns. Like Modo, the anisotropy data is encoded in the R and B channels.