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====== Spline Evaluation (Node) ======

{{ :tools:s-tk:pasted:20190808-155428.png}}

This node can evaluate [[primitive]] and return the position as well as the orientation at any position along the spline.

===== Controls =====

==== Spline ====

Allows you to pick any of the [[primitive]] in the scene to evaluate.

==== Displacement ====

This is the position on the spline. Depending on the **Displacement Type**, 0-100% is either the complete length of a spline or the first span. 100%-200% would then be the second span respectively.

==== Displacement Type ====

This determines how the **Displacement** is interpreted to evaluate the spline.

  * **Complete Spline** In this mode, the spline is taken as a whole, 0% is the start of the spline, 50% the middle of it and 100% the end.
  * **Per Span** In this mode, every successive value of 100% corresponds to a span. For example, an open spline has five knots - which is four spans. 400% would then be the and of the spline. 250% would evaluate half way between the third and the fourth knot.



==== Look Ahead ====

If Look Ahead is off, the rotation will align to the spline at the current position.

If Look Ahead is turned on, the rotation will be align to a different position on the spline, depending on the value of **Look Ahead Displacement**.

==== Look Ahead Displacement====

If **Look Ahead** is enabled, this determines how far ahead (or back) along the spline the point is that the rotation aligns to. This is using the same units as **Displacement** and also depends on **Displacement Type**.

This value is added to the current position.

==== World Coordinates ====

Computes the point on the spline and the orientation in world as opposed to object coordinates.
==== Pre/Post Behaviour ====

Determines what happens if the displacement would evaluate before the start or beyond the end of the spline respectively.

These options are only available for open splines:

  * **Hold** Holds the position at the start or the end of the spline respectively.
  * **Loop** Loops the position on the spline.
  * **Mirror** Mirrors the position on the spline.

==== Position ====

The positions computed by the node may be modified here.
The input position is either the position connected to the Position input on the node or the values set in the **Position** control.

=== X/Y/Z Mode ===

  * **Replace** (default) The position value of the axis is overwritten with the value computed by the node.
  * **Ignore** The computed position on the spline is ignored and the original value passes through.
  * **Add** The computed value on the spline is added to the position. 
  * **Multiply** The computed value on the spline is multiplied by the position.

=== Position ===

A position that may be modified or overridden by the spline evaluation.

==== Rotation ====
The rotation computed by the node may be modified here.
The input rotation is either the rotation connected to the Rotation input on the node or the values set in the **Rotation** control.

=== Heading/Pitch/Bank Mode ===

  * **Replace** (default) The rotation value of the axis is overwritten with the value computed by the node.
  * **Ignore** The computed rotation on the spline is ignored and the original value passes through.
  * **Add** The computed value on the spline is added to the rotation. 

=== Rotation ===

A rotation that may be modified or overridden by the spline evaluation.