Apply Field to Curve

Functionality

This node generates a Curve object by taking another Curve and “bending” it according to some Vector Field. More precisely, it generates a curve, each point of which is calculated as x + Coefficient * VectorPoint(x).

Optionally, for NURBS and NURBS-like curves, this node can apply a Vector Fields to control points of NURBS curve, instead of applying to all points of the curve. Such mode is supported for the following types of curves:

• NURBS curves

• Bezier curves

• Cubic splines

• Polylines

• Circular arcs

• Line segments

Some nodes, that output complex curves composed from simple curves (for example, “Rounded rectangle”), have NURBS output parameter; when it is checked, such nodes output NURBS curves, so “Apply Field to Curve” can work with them.

If this mode is enabled, then output curve will be always a NURBS curve.

Note that mathematically, for NURBS and Bezier curves, if you apply an affine transformation (such as translation, scale, rotation - i.e. vector field defined by a Matrix) to control points of a NURBS curve, you will have a curve of exactly the same shape, but translated / scaled / rotated according to the transformation. For any more complex transformation (attractor field, for example), the resulting curve will have different shape; and also it will be different from a curve that you would receive if you applied the vector field to all points of the curve instead.

Curve domain: the same as the domain of curve being deformed.

Inputs

This node has the following inputs:

• Field. Vector field to be applied to the curve. This input is mandatory.

• Curve. Curve to be “bent” by vector field. This input is mandatory.

• Coefficient. Vector field application coefficient (0 means vector field will have no effect). The default value is 1.0.

Parameters

This node has the following parameter:

• Use Control Points. If checked, then the vector field will be applied to control points of a NURBS curve, instead of applying it to all points of the curve. This node will fail (become red) if this mode is enabled, but input curve is not a NURBS and can not be presented as a NURBS. If not checked, then the node will apply the vector fields to all points of the curve; in such a case, it can process any type of curve. Disabled by default.

Outputs

This node has the following output:

• Curve. The curve modified by vector field.

Example of usage

Several Line curves modified by Noise vector field:

• Generator-> NGon

• Curves->Curve Primitives-> Line (Curve)

• Curves-> Evaluate Curve

• Fields-> Noise Vector Field

• Viz-> Viewer Draw

Apply Attractor field to control points of a NURBS curve. Control polygon of a resulting curve is indicated with red:

• Curves-> Interpolate NURBS Curve

• Curves-> Evaluate Curve

• Curves->Curve NURBS-> Deconstruct Curve

• Fields-> Attractor Field

• Vector-> Vector sort

• Viz-> Viewer Draw

• Scene-> Objects In Lite

If we apply the same curve to all points of curve (disable “Use control points” mode), we will have different curve: