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Curve Editing

This page covers the basics of curve editing. Curve basics, selecting and advanced editing are covered in the following pages:

Curve Display

Display Options

Curve Display panel

When in Edit mode, the Properties Shelf (N) contains options in the Curve Display panel for how curves are displayed in the 3D viewport.

Handles
Toggles the display of Bezier handles while in edit mode. This does not affect the appearance of the curve itself.
Normals
Toggles the display of Curve Normals.
Normal Size
Sets the display scale of curve normals.

Hiding Elements

When in Edit mode, you can hide and reveal elements from the display. This can be useful in complex models with many elements on the Screen.

Hide Selected elements
Use H, or the Curve » Show/Hide » Hide Selected menu option from the 3D window header.
Show Hidden elements
Use AltH, or the Curve » Show/Hide » Show Hidden menu option from the 3D window header.
Hide Unselected elements
Use ⇧ ShiftH, or the Curve » Show/Hide » Hide Unselected menu option from the 3D window header.



Basic Curve Editing (translation, rotation, scale)

Mode: Edit mode

Hotkey: G/R/S

Menu: Curve » Transform » Grab/Move, Rotate, Scale, …

Like other elements in Blender, Curve control points can be grabbed/moved (G), rotated (R) or scaled (S) as described in the Basic Transformations section. When in Edit mode, proportional editing is also available for transformation actions.

Snapping

Mode: Edit mode

Panel: Curve Tools (Editing context)

Mesh snapping also works with curve components. Both control points and their handles will be affected by snapping, except for within itself (other components of the active curve). Snapping works with 2D curves but points will be constrained to the local XY axes.

Deforming Tools

Mode: Edit mode

Menu: Curve » Transform

The To Sphere, Shear, Wrap and Push/Pull transform tools are described in the Transformations sections. The two other tools, Tilt and Shrink/Fatten Radius are related to Curve Extrusion.

Smoothing

Mode: Edit mode

Hotkey: W » smooth

Curve smoothing is available through the specials menu. For Bézier curves, this smoothing operation currently only smooths the positions of control points and not their tangents. End points are also constrained when smoothing.

Mirror

Mode: Edit mode

Hotkey: CtrlM

Menu: Curve » Mirror

The Mirror tool is also available, behaving exactly as with mesh vertices,


Set Bézier Handle Type

Mode: Edit mode

Panel: Curve Tools » Handles

Hotkey: V

Menu: Curve » Control Points » Set Handle Type

Handle types are a property of Bézier curves. and can be used to alter features of the curve. For example, switching to Vector handles can be used to create curves with sharp corners. Read the Bézier curves page for more details.

Extending Curves

Mode: Edit mode

Hotkey: CtrlLMB Template-LMB.png or E

Menu: Curve » Extrude

Once a curve is created you can add new segments (in fact, new control points defining new segments), either by extruding, or placing new handles with CtrlLMB Template-LMB.png clicks. Each new segment is added to one end of the curve. A new segment will only be added if a single vertex, or handle, at one end of the curve is selected. If two or more control points are selected, a new Bézier closed curve is started.

Unlike mesh editing, you cannot create a new curve inside the edited object by CtrlLMB Template-LMB.png-clicking without any control points selected. to do so, you can cut an existing curve in two parts (by deleting a segment), copying an existing one (⇧ ShiftD), or add a new one through the menu.

Subdivision

Mode: Edit mode

Panel: Curve Tools (Editing context)

Hotkey: W

Menu: Curve » Segments » Subdivide

Curve subdivision simply subdivides all selected segments by adding one or more control points between the selected segments. To control the number of cuts, press W to make a single subdivision. Then press F6 to bring up the Number of Cuts menu.


Duplication

Mode: Edit mode

Hotkey: ⇧ ShiftD

Menu: Curve » Duplicate

This command duplicates the selected control points, along with the curve segments implicitly selected (if any). The copy is selected and placed in Grab mode, so you can move it to another place.

Joining Curve Segments

Mode: Edit mode

Hotkey: F

Menu: Curve » Make Segment

Two open curves can be combined into one by creating a segment between the two curves. To join two separated curves, select one end control point from each curve then press F. The two curves are joined by a segment to become a single curve.

Curves before and after joining

Additionally, you can close a curve by joining the endpoints but note that you can only join curves of the same type (i.e. Bézier with Bézier, NURBS with NURBS)

Separating Curves

Mode: Edit mode

Hotkey: P

Menu: Curve » Separate

Curve objects that are made of multiple distinct curves can be separated into their own objects by selecting the desired segments and pressing P. Note, if there is only one curve in a Curve object, pressing P will create a new Curve object with no control points.

Deleting Elements

Mode: Edit mode

Hotkey: X or Del

Menu: Curve » Delete...

The Erase pop-up menu of curves offers you three options:


Selected
This will delete the selected control points, without breaking the curve (i.e. the adjacent points will be directly linked, joined, once the intermediary ones are deleted). Remember that NURBS order cannot be higher than its number of control points, so it might decrease when you delete some control point. Of course, when only one point remains, there is no more visible curve, and when all points are deleted, the curve itself is deleted.
Segment
This option is somewhat the opposite to the preceding one, as it will cut the curve, without removing any control points, by erasing one selected segment.
This option always removes only one segment (the last “selected” one), even when several are in the selection. So to delete all segments in your selection, you’ll have to repetitively use the same erase option…
All
As with meshes, this deletes everything in the object!


Deleting Curve Selected
Deleting Curve segments

Opening and Closing a Curve

Mode: Edit mode

Hotkey: AltC

Menu: Curve » Toggle Cyclic

This toggles between an open curve and closed curve (Cyclic). Only curves with at least one selected control point will be closed/open. The shape of the closing segment is based on the start and end handles for Bézier curves, and as usual on adjacent control points for NURBS. The only time a handle is adjusted after closing is if the handle is an Auto one. (Open curve) and (Closed curve) is the same Bézier curve open and closed.

This action only works on the original starting control-point or the last control-point added. Deleting a segment(s) doesn’t change how the action applies; it still operates only on the starting and last control-points. This means that AltC may actually join two curves instead of closing a single curve! Remember that when a 2D curve is closed, it creates a renderable flat face.

Open and Closed curves.

Switch Direction

Mode: Edit mode

Hotkey: W » 2 NumPad

Menu: Curve » Segments » Switch Direction, Specials » Switch Direction

This command will “reverse” the direction of any curve with at least one selected element (i.e. the start point will become the end one, and vice versa). This is mainly useful when using a curve as path, or using the bevel and taper options.


Converting Tools

Converting Curve Type

Mode: Edit mode

Panel: Curve Tools»Set Spline type

Set Spline Type button

You can convert splines in a curve object between Bézier, NURBS, and Poly curves. Press T to bring up the Toolshelf. Clicking on the Set Spline Type button will allow you to select the Spline type (Poly, Bézier or NURBS).

Note, this is not a “smart” conversion, i.e. Blender does not try to keep the same shape, nor the same number of control points. For example, when converting a NURBS to a Bézier, each group of three NURBS control points become a unique Bézier one (center point and two handles).

Convert Curve to Mesh

Mode: Object mode

Hotkey: AltC

Menu: Object » Convert to

There is also an “external” conversion, from curve to mesh, that only works in Object mode. It transforms a Curve object in a Mesh one, using the curve resolution to create edges and vertices. Note that it also keeps the faces and volumes created by closed and extruded curves.

Convert Mesh to Curve

Mode: Object mode

Hotkey: AltC

Menu: Object » Convert to

Mesh objects that consist of a series of connected vertices can be converted into curve objects. The resulting curve will be a Poly curve type, but can be converted to have smooth segments as described above.


Curve Parenting

Mode: Edit mode

Hotkey: CtrlP

You can make other selected objects children of one or three control points CtrlP, as with mesh objects.

Select either 1 or 3 control points, then CtrlRMB Template-RMB.png another object and use CtrlP to make a vertex parent.


Hooks

Mode: Edit mode

Hotkey: CtrlH

Menu: Curve » control points » hooks

Hooks can be added to control one or more points with other objects.

Set Goal Weight

Mode: Edit mode

Menu: W » Set Goal Weight

Set Goal Weight
This sets the “goal weight” of selected control points, which is used when a curve has Soft Body physics, forcing the curve to "stick" to their original positions, based on the weight.