CurvesTangents

Adds a tangent primitive variable to curves, giving the direction of travel along the curve at each vertex position.

user

Container for user-defined plugs. Nodes should never make their own plugs here, so users are free to do as they wish.

out

The processed output scene.

enabled

The on/off state of the node. When it is off, the node outputs the input scene unchanged.

in

The input scene

filter

The filter used to control which parts of the scene are processed. A Filter node should be connected here.

mode

The method used to compute the tangents. Each has its pros and cons.

• CentralDifference (Vertex) : The vector between the previous vertex and the next one. This is well defined for all values of curve basis and wrap, and is identical in direction to the true derivative for CatmullRom curves. Hence it is a good default.

• Derivative (Varying) : The true derivative of the curve, calculated at the end of each segment. While exact, this is not always useful, due to not being defined at each vertex position. Best used for pinned curves, where Varying and Vertex values are equivalent.

• FirstDifference (Vertex) : The vector from one vertex to the next. May be of use for linear curves.

normalize

Normalizes the tangents, so they all have unit length.

position

The name of the primitive variable containing the positions used to compute tangents. Defaults to P, but can be set to an alternative such as Pref to compute tangents from reference positions.

tangent

The name of the output primitive variable that will contain the computed tangent vectors.