# Blender 3D: Noob to Pro/Intro to Bezier Curves



Note: Some pictures are outdated.

## Bézier Curves

!It should look like
this.{width="300"}

-   First start a new Blender project, and delete the default cube.
-   Press:  → Curve → Bezier to
    create a new curve. Switch to top view
     for a clearer look. You may want
    to zoom in a bit as well.  into Edit
    mode.

The black line with the extra angled lines like centipede legs coming
off it is the Bézier curve. The white or orange dots are the *control
points*, with the ones in the middles of the pink handle lines defining
the endpoints of the curve segment.

Press  to deselect the selection, so
that all the control points turn black, and the lines connecting them
turn red. You can  on any point to
select it; however, selecting a curve endpoint selects the entire handle
line passing through it.

You can move a selected point in the usual way, with
: note how moving an endpoint causes
the curve to bend so it always connects to the endpoint. Moving just a
point at the end of a control handle affects the inner part of the
curve, making it bend more or less sharply away from the endpoint: try
moving one of these points around, and note how the handle gets longer
or shorter, and automatically rotates as necessary to remain a single
straight line.

Alternatively, you can select an endpoint (which selects the entire
control handle, remember) and use  to
rotate the handle, and  to make it
longer or shorter.

### Resolution

![](Blender267CurveDataContextBezier3D.png "Blender267CurveDataContextBezier3D.png")
In the Curve Context
![](Blender267CurveDataContextButton.png "Blender267CurveDataContextButton.png")
in the Properties window, further down you will see the Active Spline
panel. (This is only visible in Edit mode.) Note the editable field next
to the label "Resolution:", probably showing "U: 12". That number
governs the number of straight-line segments that the curve is converted
into for rendering purposes; the more of these, the smoother the result,
but it will add a bit to the render time.

This resolution setting is also used when converting the curve to a mesh
().

### Extending Your Curve

So far your Bézier curve only has one segment. You can add segments in
several different ways:

-   Back in EDIT mode,  on an endpoint
    at either end of the whole curve, and use
     to extend a new curve segment
    connected to the same endpoint. (We won't say "extrude", to avoid
    confusion with a different extrusion function discussed further
    down.)

-       on an endpoint at either end of the whole curve, and
     where the endpoint of the new
    segment will go; the new segment will immediately be added between
    the previous endpoint and the new one.

-   Select the endpoints of a single curve segment, press
     and choose "Subdivide" from the
    menu. This splits the curve segment into two new connected segments.

Note that if you  when the
selection is not precisely one endpoint of the whole curve, it will add
a new handle that is not connected to any part of the existing curve.
You can extend from this handle to create a whole set of new curve
segments that are still part of the same curve object, even though there
are no lines running between this piece of curve and the previous one.
You can join two separate pieces of the curve with a new segment by
selecting an endpoint of each and pressing
.

You can also add new pieces with 
in Edit mode.

### Removing Points and Segments

You can delete any control points by selecting them and using the
familiar  or
. The menu that pops up asks you if you
want to remove the "Selected" points, the "Segment", or "All".

-   "Selected" removes all points that are part of the same handle(s) as
    the selected point(s). Removing an endpoint of a curve piece removes
    the connected segment. Removing an interior endpoint causes the
    replacement of the curve segments on either side of it with a new
    one running directly between their remaining endpoints. Thus, the
    curve piece of which that segment was a part remains a single curve
    piece afterwards.
-   "Segment" removes a segment between two connected endpoints. If
    neither endpoint was an endpoint of the curve piece, then the
    remainder of that piece of the curve becomes two disconnected
    pieces.
-   "All" removes *all* of the control points, leaving an empty curve
    object!

### Handle Types

So far, all the handles on your curve have been *aligned*. This means
that adjacent curve segments are guaranteed to join smoothly. If you
select a control point and press , you
will get a menu allowing you to set other types for the handle:

-   *Free* means the two parts of the handle on either side of the
    endpoint are free to rotate independently, so the two curve segments
    can now meet at a corner.
-   *Vector* means the selected part of the handle points at the other
    endpoint of the same curve segment, and will keep pointing that way
    even if you move either endpoint. If you set the part of the handle
    from the other endpoint pointing back this way to "Vector" as well,
    then the curve segment becomes a straight line. However, as soon as
    you explicitly move the handle itself, it reverts to being "free".
-   *Automatic* is like "aligned", except Blender will automatically
    adjust the orientation of the handles as you move the endpoints, to
    try to keep the curve smooth. Moving either end of the handle will
    change it back to "aligned" type.

### 2D Versus 3D

At the top of the Shape panel in the Curve Context
![](Blender267CurveDataContextButton.png "Blender267CurveDataContextButton.png")
in the Properties window, you will see buttons labelled "2D" and "3D".
"2D" means the points of the curve are constrained to lie in a single
plane, while "3D" means they are free to be located anywhere in 3D space
relative to each other. Initially "3D" should be selected.

Try moving one point along the Z axis. Now click the "2D" button, and
you should see all the points you moved snap back into the same plane as
the rest. Also the "centipede legs" along the curve should have
disappeared (their presence indicates a 3D curve). You can alter the
orientation of this plane by bing into
Object mode and then rotating  the
whole curve about any desired axis.

### Closing, Filling and Extruding

Each curve piece can be individually *closed*, meaning that an extra
curve segment is automatically added between the two endpoints of the
piece. This is governed by the "Cyclic: U" checkbox in the Active Spline
panel in the Curve Context
![](Blender267CurveDataContextButton.png "Blender267CurveDataContextButton.png").
Each closed piece of a 2D curve is automatically filled to form a flat
surface.

The curve can also be *extruded* into the third dimension, effectively
turning it into a ribbon-like shape. Look for the "Extrude:" editable
field in the Geometry panel, and put a nonzero value into that to
specify the extrude width.

If you extrude a 2D closed curve, the flat surface becomes a solid
object, and the result is a *prism*---a solid shape with a uniform, but
arbitrarily complicated, cross-section.

### Scaling and Tilting

Turn your curve into a ribbon by specifying a nonzero Extrude value.
Change your view so it is not exactly from the top or bottom, but at
some angle. Notice how the ribbon is of constant width and always
perpendicular to the plane of your curve.

Select an endpoint, and press . As
you move the mouse, you are changing the *radius* of the endpoint from
its default 1.0 value, and this causes a corresponding scale factor to
be applied to the width of the ribbon at that point. You can see (and
also edit) this radius value in the Properties Shelf
, in the Transform panel at the top.

With an endpoint selected, now try
 (**Note:** This only has an
effect with 3D curves, not 2D ones). Now as you move the mouse, you are
applying a *tilt angle*, which correspondingly alters the angle of the
ribbon at that point. This value is also accessible in the Transform
panel in the Properties Shelf.

The scale radius and tilt become particularly useful when you apply a
*bevel shape* to the curve---then you will start to get much more
complicated shapes than simple ribbons.

## NURBS Curves

![](Blender267NURBSPointTransform.png "Blender267NURBSPointTransform.png")
Start a new Blender document, and get rid of the default cube.

This time, do  → Curve → Nurbs
Curve, and  into Edit mode. The result
looks a bit similar to a Bézier, except there are no control handles,
only the segment endpoints. Instead of dragging handles, you can adjust
a weighting assigned to each control point. Bring up the Properties
Shelf with  if it is not already
visible. If you have a single point selected, in the Transform panel at
the top, you should see four editable fields under the heading "Control
Point:", labelled "X:", "Y:", "Z:", and "W:". The first three are of
course the position of the point; the "W" value is like a gravitational
field strength that attracts the curve to the point. Try adjusting this,
and see how it influences the shape of the curve near that point.

You can move endpoints in the usual way, but there are no handles to
rotate. All the other options for add and deleting endpoints apply as
for Bézier curves:  or
xtend,
→Subdivide,
eting Select/Segment/All. The curve can
be 2D/3D, extruded and cyclic, and each endpoint has a
cale radius and a
ilt angle. In the "Active Spline"
panel in Object Properties, there is an additional "Endpoint: U"
checkbox which forces the curve to pass through the endpoints (this is
ignored if Cyclic is enabled).

→Curve→Nurbs Circle inserts a NURBS curve with eight control points
arranged in a square, "Cyclic: U" enabled, and the weights of the corner
points adjusted so the curve is an exact circle.

→Curve→Path inserts a NURBS curve with five control points in a straight
line, and the "Endpoint: U" option already checked.

## Which Curves To Use?

As mentioned earlier, NURBS curves are heavily used in CAD applications,
while Béziers are popular in 2D drawing applications. If you are
importing data from these applications, then you won't have any choice
about which one you end up with.

But if you are creating your own curves, then you have a choice. If you
have done drawing with Bézier curves a lot, then you should feel at home
with them. If you just want simple curves to deform a shape or guide an
animation, NURBS curves could very well do the trick---you could even
leave the W values at the default, and just add, delete and position
points to get a suitable curve.

## Extruding from 2D to 3D

You may have noticed you can only modify the curve in two dimensions,
and now it\'s time to explore the third dimension! Extruding is where
you define a two dimensional \'profile\' shape, and it is \'swept\'
through space to create a volume.

**Noob note** Bézier circles are not true circles, they are
approximations. For artistic purposes, this may not really matter, but
for precision modelling only NURBS circles should be used. This is due
to the math used to describe the Bézier and NURBS curves.

## Make a Simple Face of Bézier Curves

-   **Make a curve and fill it**: Being sure you are in 2D mode, Use the
    steps above to create something simple, and fill it in using

.

**Noob note:** you may find it easier to use Bézier circles, instead of
filling discrete curves.

![](Face_Bezier_Curve.png "Face_Bezier_Curve.png"){width="400"}

Note that the eyes and mouth of the face above are parts of the same
curve object. Blender can only identify holes in a filled curve if the
holes are part of the same object as the outer curve. If you had created
four separate curves then filling the outer curve would have covered the
eyes and mouth. To create a detached section of a curve, be in edit mode
and deselect all the points (). Then
create new points (you will need two or three) with
+.
Alternatively you can create the pieces as separate curve objects and
join them later with  in object
mode. You might prefer the alternative way if you don\'t want a lot of
control handles and \"centipede legs\" to distract you.

### Extrude the Simple Face

![](Curve_and_Surface_Box.png "Curve_and_Surface_Box.png")

**Set the extrude depth**: Click on the Object Data button and find the
Geometry panel. (Older versions: find the \'Curve and Surface\' box in
the Editing tab of the Buttons window.) There is a slider called
Extrude. Set the Extrude depth to something other than 0, and probably
less than 1.

!Bezler
Geometry\|right\|300px

Behold, your 2d curve has transformed into a neat 3d structure. The
great thing is, you can still edit the curve as if it were just 2d, and
the changes will update in real time.

### Bevel the Simple Face

Now you have an extruded shape, you should start playing around with
some of the other curve settings on offer, so here is a description of
how the Bevel depth and Bevel resolution sliders work.

Try setting the Bevel depth to a small value, say 0.02. This will cut
off all of the sharp edges, and give a bevelled effect all around the
shape.

![](Bezier_Face_Bevel.png "Bezier_Face_Bevel.png"){width="400"}

As you may guess, Bevel resolution decides how many times the algorithm
divides up an edge. Higher values than 0 result in smooth curves rather
than sharp edges, but dramatically increase the number of vertices in
the shape.

Try setting the resolution to 3 or 4, you should see an effect like
this:

![](Bezier_Face_Bevel_4.png "Bezier_Face_Bevel_4.png"){width="400"}

