# Blender 3D: Noob to Pro/NURBS Patches

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What Blender calls *surfaces* are more commonly referred to in computer
graphics as *patches*. It makes sense to stick to the commonly-accepted
terminology, particularly when talking with users of other software.

You previously saw how a NURBS curve consisted of a single row of any
number of control points. A NURBS patch consists of an *n*-by-*m* grid
of points, where *n* and *m* can be any positive integer (and not
necessarily equal). The grid has a rectangular topology, but of course
the points may be positioned anywhere in space, to shape the curve
accordingly. The resulting object can look a bit like a mesh in edit
mode, but it behaves very differently.

## Your First NURBS Patch

![](Blender267SurfaceDataContextNURBS.png "Blender267SurfaceDataContextNURBS.png")
Start a new document, delete the default cube, bla-bla-bla, but stay in
Object mode. Add a new NURBS surface:
→Surface→NURBS Surface. Switch to
Edit mode, and find the Surface Context
![](Blender267SurfaceDataContextButton.png "Blender267SurfaceDataContextButton.png")
in the Properties window.

For NURBS curves, you previously had the "Cyclic: U" and "Endpoint: U"
options for making the curve open or closed, and extending all the way
to the endpoints or not. Now you also have "Cyclic: V" and "Endpoint:
V", because the surface has two dimensions, and you can control these
settings independently along each dimension. Try checking just one
Cyclic box at a time, and the patch turns into a closed ribbon shape
along the corresponding dimension; check both, and it forms a solid
object, shaped perhaps reminiscent of a pillow or an unusual loaf of
bread.

As with the curve case, you can move selected points around to alter the
shape of the curve, and adjust the "W" value of each point to control
how strongly it attracts the curve. Radius-scaling and tilt settings are
still adjustable, but don't seem to achieve anything, since you can't
apply a bevel to a surface.

### Adding and Removing Control Points

Adding and deleting points in a NURBS surface need to follow some rules.
The irritating thing is, if you try to do things not in accordance with
these rules, Blender will simply ignore you, with no error message.

Remember how I said that the control points form a *n*-by-*m*
rectangular grid? Any addition or deletion of points must preserve this
characteristic. Thus, you can only add or remove points an entire row or
column at a time. For example, to extend the patch, you select all the
points along one outermost edge of it, and press
 to add the same number of new points.

Or you can select all the points in two adjacent rows or columns, and
use →Subdivide to add a new row/column
of points in-between. Similarly, you can only delete points by selecting
an entire row or column of them at a time.

### NURBS Curve, NURBS Circle?

The first two options in the
→Surface menu are "NURBS Curve" and
"NURBS Circle". Try adding these objects; at first glance, they look
exactly like the "Nurbs Curve" and "Nurbs Circle" entries in the
→Curve menu. However, regardless of
appearances, these really are surfaces, not curves.

To observe the difference, ensure all points are selected, and now use
 to extend the curve: this will create
a *whole row* of new control points, instead of just one! As with the
different options in the →Curve
menu, the ones in →Surface offer
premade objects for you to choose whichever is the most convenient
starting point for the shape you actually want to create.

