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

9 Dec 2020


      Thanks Aditya!
One can learn a lot with your answers !
In the Metafun manual I see enlonged but I did not know to use it.

Best regards: Otared
...
On 9 Dec 2020, at 21:38, Aditya Mahajan  wrote:
On Wed, 9 Dec 2020, Otared Kavian wrote:
...
Hi Aditya,
Thanks for the alternative method, which comes handy if one wishes to extend the straight line by a different amount at either end:
\starttext
\startMPcode
  z1 = (1cm,3cm) ;
  z2 = (5cm, 9cm) ;
  z3 = 1cm * dir(angle (z2 - z1)) shifted z2 ;
  z4 = -.5cm*dir(angle(z2 - z1)) shifted z1 ;
  draw z1 -- z3 ; 
  draw z4 -- z1 ;
  draw z1 -- z2 withcolor red ;
\stopMPcode
\stoptext
Or just redefine shortened to accept a pair!
\startMPdefinitions
primarydef p shortened d =
   reverse ( ( reverse (p enlonged -xpart paired(d)) ) enlonged -ypart paired(d) )
enddef ;
\stopMPdefinitions
\starttext
\startMPpage
z1 = (1cm,3cm) ;
z2 = (5cm, 9cm) ;
draw (z1--z2) shortened (-1cm,-2cm)  withcolor blue ;
draw (z1--z2) withcolor red ;
\stopMPpage
\stoptext
Now that if you really want to shorten a path, then cutends works better than shortened
\startMPdefinitions
primarydef p shortened d =
   reverse ( ( reverse (p enlonged -xpart paired(d)) ) enlonged -ypart paired(d) )
enddef ;
\stopMPdefinitions
\starttext
\startMPpage
z1 = (1cm,3cm) ;
z2 = (5cm, 9cm) ;
path p, q;
p := z1 {up} .. {right} z2;
q := p shifted (6cm, 0);
draw p withcolor red ;
draw p shortened (1cm,2cm)  withcolor blue ;
draw q withcolor green ;
draw q cutends (1cm,2cm)  withcolor blue ;
\stopMPpage
\stoptext
Aditya
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