4.2 Orientation of Segments

A segment defines two special control points referencing the first and the last control point of the segment. These points are called FirstPoint and LastPoint, respectively. Line segments consist, of course, only of a FirstPoint and a LastPoint. Spline segments consist of at least three control points, where FirstPoint and LastPoint refers to two of the points. In the case of a circular spline FirstPoint and LastPoint are identical and refer to an arbitrary control point of the circular spline. In the case of a non-circular spline FirstPoint and LastPoint refer to the first and last point in the spline, respectively. The result of this definition is that a segment is said to have a direction from FirstPoint to LastPoint.

When segments are used in construction of a shape, the segments are connected in such a way that LastPoint of a segment is connected to FirstPoint of the next segment. In this way the shape gets an orientation. The orientation of the shape is used to determine what is inside and what is outside of the shape. It is the inside of a shape that is filled with paint when a graphical object is drawn.

The Bifrost Graphics System - Reference Manual
© 1991-2004 Mjølner Informatics
[Modified: Wednesday October 4th 2000 at 11:39]