Local Coordinate System at a Point
Local Coordinate System at a Point
Here is a typical belt point showing the triad (well, strictly a hexad since it shows +ve and -ve axes, but that is a clumsy term) in which which the belt path can be used by the mouse. These are the local axes at that belt point, it is along these local axes that the point can be dragged and about them that it can be twisted.
All six axes are shown at a point.
By default display of this triad treats the belt material as being about 30% transparent so that symbols "behind" the belt can still be seen and used. The symbols that are shown and the %age transparency can be controlled in the "Path visualisation" panel.
How the local coordinates are derived
The path is projected outwards from the base path point where the "outwards" vector is determined either from the outward normal of nearby structure ("local normal") or from the curvature of the belt path itself ("path twist").
The "along the belt" vector, red, is determined
from the line along the basic path from point to point. The +ve direction
is from point P to point P+1.
The "transverse" vector, green, is at right angles to these
two vectors.