# Active Spline¶

Reference

Mode: | Edit Mode |
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Menu: |

The *Active Spline* panel is used in Edit Mode to control properties of the currently selected spline.

- Cyclic U/V
- Like curves, surfaces can be closed (cyclical) or open, independently in both directions,
allowing you to easily create a tube, donut or sphere shape,
and they can be viewed as “solids” in
*Edit Mode*. This can be set per interpolation axis. - Bézier U
- Makes the surface act like a Bézier curve.
The control points act like
*Free*handles of a Bézier curve. Depending on the*Order*, 3 or 4 control points form one spline segment. This can be set per interpolation axis.*Cyclic*and*Endpoint*must be disabled for this option to work. - Endpoint U/V
Makes the surface contact the end control points. This can be set per interpolation axis.

*Cyclic*must be disabled for this option to work.In the image below, the U interpolation axis is labeled as “U” and the V interpolation axis is labeled as “V”. The U’s interpolation axis has been set to

*Endpoint*and as such the surface now extends to the outer edges from E1 to E2 along the U interpolation axis.To cause the surface to extend to all edges,

*Endpoint*would be set for the V’s axis as well.- Order U/V
This property is the same as with NURBS Curves; it specifies how much the control points are taken into account for calculating the curve of the surface shape. For high Orders 1 the surface pulls away from the control points, creating a smoother surface by assuming that the

*Resolution U/V*is high enough. For lowest Orders 2 the surface follows the control points, creating a surface that tends to follow the grid cage.For illustration purposes, in both Fig. Order 2 and Order 4 surface., the knot vectors were set to

*Endpoint*, causing the surface to extend to all edges.You can set independently the order for each interpolation axis, and like curves, it

**cannot**be lower than 2, and higher than 6 or the number of control points on the relevant axis.- Resolution U/V
- Alters the resolution of each segment by changing the number of subdivisions. This can be set per interpolation axis.
- Smooth
- Use Smooth Shading for any 3D geometry.