The W Coordinate texture is a way to access the OctaneRender® W Coordinate system, which provides the means to place gradients on hair geometry. It stores an inherent hair gradient interpolation along with hair data exported from common 3D modelling applications. It takes into account the basis of the interpolation set in an Octane Obj Params tab attached to a scene object (Figure 1). When you plug the W Coordinate into a Gradient texture as the Input texture, it tells OctaneRender to render the inputs as a gradient mapping based on either the hair length or the segment count per strand.
Figure 1: The Fur tab in an Octane Obj Parms tab
Figure 2 displays a Houdini® hair system rendered with the W Coordinate, and applied to a Gradient node that is connected to a DiffuseAmount of diffusion, or the reflection of light photons at different angles from an uneven or granular surface. Used for dull, non-reflecting materials or mesh emitters. material’s Diffuse parameter.
Figure 2: A Houdini hair system rendering using the W Coordinate to distribute colors across the hair stand length
Figure 3: The Gradient node parameters and the node network associated with the rendering from Figure 2