Rotating Strands 

The Rotate Strands operator sets the twist of individual strands - the rotation of each strand around its own stem. For ordinary cylindrical hair this rotation does not matter, but it becomes important whenever a strand has a defined facing direction or when other operators act around the strand's stem.

 

When twist matters 

Two common cases need a defined twist:

• Skinning geometry along strands: when you use Rendering Hair as Mesh Geometry to attach a flat billboard or proxy mesh along each strand, the twist decides which way that geometry faces. This is essential for cards, feathers, and leaves.
• Operations around the stem: effects such as curling are computed relative to the strand's starting rotation, so setting the twist controls how they sit.

 

Controlling rotation 

You can orient strands in a particular direction - for example facing toward the distribution surface - or give them random orientations for a more natural, scattered look. As with other operators, a strand group limits the effect, and the rotation can be varied with maps and strand channels.

 

Related 

• Rendering Hair as Mesh Geometry - where strand facing is most visible.
• Curl Operator - depends on strand starting rotation.

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