[NTG-context] Metafun: how to draw a straight line past the end points

Fabrice L fabrice.alpha at gmail.com
Wed Dec 9 17:19:59 CET 2020


> Le 9 déc. 2020 à 10:57, Otared Kavian <otared at gmail.com> a écrit :
> Hi,
> I have a silly question: given two points in the plane
> 	z1 = (1cm,3cm) ;
> 	z2 = (5cm, 9cm) ;
> the command
> 	draw z1 -- z2 withpen pencircle scaled .5pt ;
> draws the line segment joining z1 and z2. How could I draw the line segment which goes a little further (say 1cm) than both the end points of this segment (that is in this example, a point before z1 and a point after z2 on the straight line) .
> Indeed it is possible to write the equation of the line and then compute by hand the coordinates of the new end points, but I think there is a simpler way in Metafun to do this.

The shortened operation is the solution ! See MetaFun manual section 1.18

z1 = (1cm,3cm) ;
z2 = (5cm, 9cm) ;
draw (z1--z2) shortened -1cm  withcolor blue ;
draw (z1--z2) withcolor red ;


> Thanks for any help: Otared
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