The Curve operation creates polygons, NURBS and Bezier curves.
The Curve operation creates polygons, NURBS and Bezier curves.
To build a curve, click with the left mouse button to specify the data
points, then 
to finish. ⇧ Shift + 
close to any end of the
curve to extend the curve in that direction by adding new points. For
added precision, bring up the operation dialog from the viewer menu or
by typing ${h.pane.gview.operation_parameters}, then type the points
one by one, clicking on “Add Point” to add each point.
See the Ctrl + menu for a full list of options. Any options
chosen from that menu will be remembered the next time you start a new
curve operation. For example, if you want to always create NURBS curves,
choose “NURBS curve” from the Ctrl + menu. Alternatively,
choose “NURBS” from the Primitive Type menu above the viewport, the
on that menu to make the NURBS option the current default
(see “Make Current Value Default”).
If you are building a NURBS or Bezier curve, the data points can be interpreted as control vertices (CV's), breakpoints, or freehand points. A curve built with breakpoints will run through each of the breakpoints.
To reference other geometry (points or breakpoints) such that any
changes in that geometry will reshape the curve built in this operation,
turn on snapping to points and/or breakpoints and enable Snap
Consolidate in the Snap Options dialog above the viewport. Referencing
the breakpoints of other curves is a good way of building smart curve
networks. You can always convert all references to numerical coordinates
using the Ctrl + menu.
When snapping to primitives, it is possible to snap to the curve you are building. This may sometimes be undesirable. To avoid self-snapping lower the gravity entry in the Snap Options.
The points created with this operation are not individually animatable here. Append a Transform operation or other deformers to animate the curve points.