The W Coordinate texture can access the OctaneRender® W Coordinate System, which provides the means to place Gradients on hair geometry. The hair geometry stores an inherent Hair Gradient Interpolation along with hair data exported from common 3D modeling applications. W is an attribute of the Mesh node, which defines a coordinate for every hair vertex per strand. This attribute is loaded from an AlembicAn open format used to bake animated scenes for easy transfer between digital content creation tools. file input. However, if the attribute is not in the Alembic file, OctaneRender creates the coordinates automatically per strand. OctaneRender uses the resulting vertex coordinates to distribute a gradient per strand, and the gradient interpolation is based on settings in the Import tab of the Preferences pane.
It takes into account basis of the Interpolation set in the Import tab.
To use the W attribute to apply gradient colors to the hair data, you must plug a W Coordinate texture as the Input of an OctaneRender Gradient . This tells OctaneRender to render the inputs as a Gradient mapping, and OctaneRender uses the specified Gradient interpolation to distribute the gradient. This is based on either the hair length or the segment count per strand, depending on what is set in the Import tab for hair geometry.
For example, if the hair strand has 3 segments, and each of the hair segments have a different length, the Hair Length option distributes the W evenly from root to tip. Segment Count distributes the W independent of the segment lengths, so the first segment goes from 0 to 1/3, the second segment goes from 1/3 to 2/3, and the last segment goes from 2/3 to 1.
Hair Segment Interpolation |
Hair Length Interpolation |