Paths in PlotDevice are made up of cubic Bezier curves. Beziers are commonly used in computer graphics to draw smooth contours. The first handle describes the forward curvature of the starting point, the second handle the backward curvature of the ending point. By default, the path would be filled black and drawn without a stroke color. The fill and stroke arguments override these to give us just the line itself. Note that the initial point , is set as part of the bezier call, while the destination point is the final pair of args passed to curveto.
Bezier objects give you access to all the points in a path as well as their control handles. This allows you to transform paths on the fly and even manipulate type using the textpath comand.
Additionally, you can unite and intersect different paths or perform a variety of math operations e. Each of the PlotDevice shape commands arc , poly , etc. This object is a list-like sequence of Curve objects that you can iterate over. Each element in the path is a Curve object with the following attributes:. If curve. Each control handle is a simple Point object with x and y attributes:.
The handles are useful for paths that consist of multiple Bezier curves. The ctrl1 handle controls how the curve connects to the previous point, the ctrl2 handle how the curve connects to the destination point. For example:. This is the path returned from the textpath command for the character e in the Dolly typeface. This is the same path, but modified. Note that modifying the Curve objects in the for-loop does not affect the original path.
Each of the Curve s that makes up a Bezier path has a starting point, an ending point, and control handles. What if we want to know the location of a point on the path that is not one of these endpoints, but somewhere in between? What is the location of the midpoint of an arc for example?
