drawing curves in markup (was: draw-line)

[Carl Sorensen]

2015-03-17 15:52 GMT+01:00 Kevin Barry <address@hidden>:

> If I knew more about mathematics I might know how to calculate the
>tangent to a 
> bezier curve at the end point (to know how much to rotate the arrowhead)
>and the 
> function wouldn't be such a hack.


The tangent to a bezier curve at the endpoint is the line that goes from
the endpoint to the control point.  It's really easy to get if you have
the bezier definition.

So for a bezier that goes from  (0,0) through (1,1) and (2,1) to (3,0),
the outward tangent at the first end is in the direction (-1,-1), and the
outward tangent at the second end is (1,-1).

HTH,

Carl