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Vector Contours

Bézier cubic curve, simple quadratic curve, line segment

Contours of vector objects digitized in Studio Next are so called splines. A spline is a piecewise-defined curve. This means it's made up of multiple curve and/or line segments joined together. Splines are very versatile for creating smooth, complex shapes.

Studio Next allows you to use these types of segments (elements) of splines:

  1. Straight line segment
  2. Simple curve (quadratic curve)
  3. Bézier curve (cubic curve)

An object in Studio Next is usually drawn with several contour elements. Elements are defined by control points called nodes.

Line and curve vector elements

Line segment (left) is defined by 2 points. A simple curve (center) is defined by 3 points. A Bézier curve (right) is defined by 4 points.

Line segment has two nodes - a start node and an end node.

Simple curves have three nodes - a start, a midpoint, and an end point. The node at the center of the curve defines the arc of the curve.

The most versatile type of curve is the Bézier curve, defined by a start and end node and two control handles between them.

Note:The middle node of the simple quadratic curve always lays on the curve. The control nodes (handles) of the cubic Bézier curve usually do not lay on the curve.

Icons of line and curve vector elements

Icons representing the respective segment types: Line segment (left), simple curve (center), Bézier curve (right)

During editing, all segment types can be converted to another type as needed. When converting to a simpler type, the shape of the segment may be simplified automatically.

Bézier curves

A cubic Bézier curve is an essential tool in computer graphics and design, commonly used to create smooth, scalable curves. It is defined by a group of control nodes, and its path is calculated through a mathematical formula based on these points. The shape of the curve is determined by the placement of these control nodes. The first and last nodes set the start and end positions of the curve. The two middle nodess, often referred to as handles, influence the direction and curvature of the curve. Bézier curves are valued for their ability to produce smooth, continuous lines, making them perfect for creating shapes in vector graphics. Since they are mathematically defined, Bézier curves can be resized to any scale without losing resolution.

The curve does not always pass through the middle two control nodes. Instead, these points serve as magnets, guiding the curve toward them. By adjusting the position of these handles, the shape and curvature of the curve can be finely tuned.

By connecting multiple cubic Bézier curves, you can create intricate outlines of any shape, from simple rounded forms to highly detailed figures.

Difference between simple quadratic curve and cubic Bézier curve

The key difference between simple quadratic curve and cubic Bézier curve lies in the number of control points they use, which directly impacts their flexibility and shape. Due to having only one control point, simple quadratic curves are less flexible in defining complex curves. Single quadratic curve can only create an U-shaped segment, while cubic Bézier curve can create both S-shaped and U-shaped segments. In general, the number of segments required to vectorize a complex edge is lower when using Bézier curves. This makes the digitizing process faster.

Quadratic versus cubic curve

The same shape requires larger number of simple quadratic curves (left) to approximate than cubic Bézier curves (right)

Note: Older versions of Studio did not support Bézier curves. Files created in older versions of Studio therefore contain only simpler quadratic curves, which are still functional. However, for new projects, it is recommended to use Bézier curves instead of simple quadratic curves. Bézier curves allow you to speed up and simplify your digitizing work. If you export your designs to .SVG format for further use in graphics programs, you will also appreciate the ability to perfectly smooth curve connections.

Smoothness

When properly constructed, Bézier splines create smooth transitions between curve segments.

On the other hand, simple quadratic curves can only form a single arc and it is difficult to create a smooth transition between them.

Studio allows you to assign a smoothness type to nodes common to consecutive pairs of Bézier curves. The assigned smoothness type is retained when the nodes are moved, which helps maintain the shape of the outline. The default type is "cusp", which means no smoothness. The second type - "smooth" means that control points of consecutive Bézier curves are automatically adjusted so that transition from one Bézier curve to the next Bézier curve is smooth. The third type is "symmetrical", which means that transition is not only smooth, but also symmetrical around the node common to both curves.

Cusp, smooth and symmetrical transition between Bézier curves

When connecting multiple Bézier curves to form splines, the nature of the transition between those segments is crucial. To make it easier to identify the type of transition, Studio displays the meeting points between the curves as nodes of different shapes.

1. Cusp

A cusp transition occurs when two Bézier curve segments meet at a sharp point, creating a sudden change in direction. Visually, it is an abrupt change in direction, often used to create sharp corners or distinct angles.

Transition between Bezier curves - cusp

Cusp transition between the Bézier curves. The common node is a diamond shape

2. Smooth transition

A smooth transition means that the two Bézier curve segments meet in such a way that there is a seamless flow from one curve to the next. The curves appear to be part of a single, continuous line and there is no abrupt change in direction. To achieve a smooth transition, the control handles of the adjacent Bézier curves must be positioned in a way that aligns their direction in the meeting point.

Transition between Bezier curves - smooth

Smooth transition between the Bézier curves. The common node is square in shape

3. Symmetrical transition

A symmetrical transition further refines the smoothness. In addition to the smoothness, there is also a sense of balanced curvature. This implies that the control points are arranged in a symmetrical pattern around the meeting point. This transition is often used for creating rounded, even shapes.

Transition between Bezier curves - symmetrical

Symmetrical transition between the Bézier curves. The common node has circular shape

Complex contours - splines

Straight and curved elements can be combined in any way to create a complex shape. Object made from straight line segments and Bezier curves

An object made from straight line segments and Bézier curves

Note: no elements should not intersect themselves or other elements in the contour. Otherwise, the compilation into stitches may fail.

Edge modeling

Bézier curves in node editing mode can be edited intuitively by dragging any part of the curve. The point on the curve under the cursor can also snap to grids, guide lines, etc., just like regular nodes.

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