Chapter 4
As the Curve Turns

Featuring

For five years now, we have looked at the title for this chapter and wondered if the time had come to replace this mildly clever double-entendre (you know...As the World Turns...that soap opera about life...curves are everything to CorelDRAW...as the curve turns, so turns life...oh, forget it).

But after close annual scrutiny, the title stays. The curve really is the lifeblood of everything that CorelDRAW does. Almost every shape you create in DRAW has curve-like properties. Rectangles and ellipses are really curves in disguise. Text characters have nodes, just like curves. Even straight lines are treated by DRAW as curves. The only type of object that DRAW doesn’t try to define as a curve is an imported bitmap. In short, if it’s a vector-based object, DRAW sees it as a curve.

A vector object always has a path that defines its shape. If the path is closed—that is, the start and end points are the same—the object also has an interior that can be filled with colors or patterns. (As of DRAW 8, you can fill open curves, but that falls under the category of knowing the rules well enough to break them; we’ll start with the fundamentals here.) All paths created in DRAW contain two components: segments and nodes. Here is how DRAW defines these terms:

•  A path represents the route from a start point to an end point. Simple closed objects, such as rectangles or ellipses, generally have a single path. If you combine several objects into one, the new object has multiple subpaths. Letters with holes, like O, are also made up of multiple subpaths. One subpath is the outer oval of the letter, and another forms the inner edge.

•  A segment is a single section of a path. It can be either a line or a curve. Each side of a rectangle, for instance, is a segment. An ellipse is a single segment. A crooked line drawn with the Freehand tool could consist of many segments.

•  A node is the little point that is the start or end point of a segment. A rectangle has four nodes; a circle has two, one on top of the other; your freehand line might have a dozen.

Every object you create in DRAW contains these three basic elements—paths, segments, and nodes—and in all cases, DRAW provides access to them for editing and reshaping. Sometimes, that access is not so straightforward, as is the case with text characters, but one way or the other, you can reach the quantum particle level of an object and see its paths, segments, and nodes in action.

When you draw with the Freehand tool, you are automatically creating lines or curves, end of discussion. But when you use the other four tools—Ellipse, Rectangle, Polygon, and Text—you create objects that DRAW treats with a bit more reverence. Ellipses, for instance, always have one continuous circumference, rectangles always have four sides, polygons maintain their symmetry, and text carries with it a host of special attributes such as typeface, style, spacing, and size.

Once you use DRAW’s Convert to Curves command, however, DRAW strips those objects of their special status; they become just curves. You then are free to add a fifth side to a rectangle, turn circles into odd shapes, and commit all sorts of unspeakable crimes on text characters.

Let’s start by looking at curves and lines; we’ll cover ellipses, rectangles, polygons, and text characters later in the chapter.

The Science of Curves and Lines

To begin exploring the dynamics of curves, click on the Freehand tool and draw a curve. Any curve will do, like the one in Figure 4.1. If the Freehand tool isn’t visible, click and hold the Curve flyout (the fourth button from the top of the toolbox). Choose the Freehand tool from the flyout.

With the object selected, you can count for yourself the number of nodes and segments that make up the curve. In Figure 4.1, 18 nodes were required, including the first and last ones, to represent the 17 segments of the curve. Notice that the curve intersects itself; that’s okay.

FIGURE 4.1  This thing may not look like much, but it can teach you quite a bit about how DRAW views nodes and segments.

Because you used the Freehand tool, your object is already a curve and can be easily altered. Once you select the Shape tool, there are three ways to change the parts of a curve:

•  Click and drag any node to move it.

•  Click and drag any segment to change the path between two nodes.

•  Click a node and then drag the control handles to change the shape of the path as it approaches that node.

Moving a segment often produces the same result as moving the control handles...but often not. The mechanics of nodes and segments make up a science that resides right next door to black magic, and trying to understand their true nature and behavior promises to be a fruitless venture. Far better for you to experiment with the three different ways to shape curves and develop a feel for them. Sometimes we suspect the developers themselves aren’t entirely sure what kind of a Frankenstein monster they’ve created.

TIP Experienced users might want to take time out to customize their status bars. Click on it with mouse Button 2, choose Customize, and then double-click Status Bar in the Toolbars list box. From selections displayed on the right side of the window, click and drag any status bar item (such as Object Details) to the status bar on the bottom of your screen display. Now watch as you select various nodes; DRAW refers to them as either line or curve nodes, and either type may be smooth or cusp. As you drew your curve, DRAW automatically decided which type of node to use at each turn.

DRAW uses smooth nodes where it finds a gradual transition from one segment to another and cusp nodes to make sharper turns. Figure 4.2 zeroes in on one of the cusp nodes of the curve we created for Figure 4.1. Notice how the curve makes a sharp downward turn. DRAW automatically used a cusp node to create this shape; we didn’t have to tell it to. Also, if DRAW senses that you went from one node to another along a straight path, it will use a straight line segment between those two nodes, instead of a curve segment.

FIGURE 4.2  DRAW sees you turning a sharp corner here, so it automatically uses a cusp node.