Curves

A curve is a one-dimensional shape, usually stored as a sequence of points. The different types of curve define the method of interpolation between these points.

A curve may be defined as simple if all its points are unique and closed if its start point is equal to its endpoint. A curve that is both simple and closed, i.e. physically appears as a polygonal shape, is called a ring.

Spline

Not currently implemented.

Arc

An arc is a curve that forms part of the boundary of an ellipse. As such it is defined by a single coordinate defining the centre of the arc and further properties describing the radius of its axes in the x and y directions.

The start point and the end point of the arc are defined by start and end angles. Extrapolation of lines at these angles from the centre of the arc, will cut the elliptical boundary at the start and end points respectively.

An arc also has a property defining its rotation from the horizontal.

Polyline

A polyline is a curve with linear interpolation between points such that each consecutive pair of points defines a line segment.