Definition: B-splines are not used very often in 2D graphics software but are used quite extensively in 3D modeling software. They have an advantage over Bézier curves in that they are smoother and easier to control. B-splines consist entirely of smooth curves, but sharp corners can be introduced by joining two spline curve segments. The continuous curve of a b-spline is defined by control points. While the curve is shaped by the control points, it generally does not pass through them. (Continued below...)

Creature House Expression and Ulead PhotoImpact are two 2D graphics programs that offer spline curve drawing tools. Drawing with a spline tool is generally more intuitive and much easier for computer drawing beginners to understand compared to drawing with a Bézier tool. Because a Bézier curve often changes form as each new curve segment is placed, it is difficult to predict the outcome unless you understand the underlying geometry. On the other hand, when drawing splines, the shape of the curve can be previewed as the pointer is moved and the curve does not change form as new segments are placed.

Originally, a spline tool was a thin flexible strip of metal or rubber used by draftsman to aid in drawing curved lines.

The solid line represents an open path created with Expression's B-Spline tool. The points on the dotted line represent mouse clicks. By moving the control points on the dotted line, the path can be reshaped.

The solid line represents a closed path created with Expression's B-Spline tool.

Just like any other path, closed shapes created with a spline tool can be stroked and filled as shown here.

The Spline tool in Ulead PhotoImpact creates a path using a spline method, but the resulting path becomes a Bezier curve and must be reshaped using nodes and control handles.

Related Terms • Path • Bezier Curve • Control Points

The Language of Curves
Whether working with curves and paths and vector-based shapes in painting or drawing software, it is helpful to understand some of the terminology used for this type of computer drawing.

Ulead PhotoImpact Resources
Tutorials and other resources for PhotoImpact users.

Creature House Expression Resources
Tutorials and other resources for Expression users.

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