question about MP drawing with dir

question about MP drawing with dir

[Pablo Rodriguez]

Dear Alan,

I have the following sample (as I wrote, this is addictive ;-)):

  \startMPpage
    draw fullcircle scaled (.06TextWidth - .05LineHeight);

    for m=1 step 2 until 10 :
        path s ; s := (dir30--dir150--dir315--dir90--dir225--cycle)
            scaled m;
        n := (m * 50) ;
        o := (m / 5) ;
        for i=0 upto n :
          draw textext("\utfchar{"EB09}")
            scaled (o * .025) shifted point (i/n*length s) of s ;
        endfor
    endfor
  \stopMPpage

dir seems magic to me. I don’t understand how it works, not even how it
can be used for drawing not having an origin.

Would it be possible that all stars are vertically centered?

How should be the path defined?

Many thanks for your help,

Pablo
-- 
http://www.ousia.tk
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Re: question about MP drawing with dir

[Hans Hagen]

On 5/24/2018 9:01 PM, Pablo Rodriguez wrote:
> Dear Alan,
> 
> I have the following sample (as I wrote, this is addictive ;-)):
> 
>    \startMPpage
>      draw fullcircle scaled (.06TextWidth - .05LineHeight);
> 
>      for m=1 step 2 until 10 :
>          path s ; s := (dir30--dir150--dir315--dir90--dir225--cycle)
>              scaled m;
>          n := (m * 50) ;
>          o := (m / 5) ;
>          for i=0 upto n :
>            draw textext("\utfchar{"EB09}")
>              scaled (o * .025) shifted point (i/n*length s) of s ;
>          endfor
>      endfor
>    \stopMPpage

reusing a picture is more efficient

\startMPpage
     draw fullcircle scaled (.06TextWidth - .05LineHeight);
     picture t ; t := textext("\cldcontext{utf.char(0xEB09)}") ;
     for m=1 step 2 until 10 :
         path s ; s := (dir30--dir150--dir315--dir90--dir225--cycle) 
scaled m;
         n := (m * 50) ;
         o := (m / 5) ;
         for i=0 upto n :
           draw t scaled (o * .025) shifted point (i/n*length s) of s ;
         endfor
     endfor
\stopMPpage




-- 

-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------
___________________________________________________________________________________
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___________________________________________________________________________________

Re: question about MP drawing with dir

[Hans Hagen]

On 5/24/2018 9:33 PM, Hans Hagen wrote:

>      picture t ; t := textext("\Ux{EB09}")
-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------
___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!

maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage  : http://www.pragma-ade.nl / http://context.aanhet.net
archive  : https://bitbucket.org/phg/context-mirror/commits/
wiki     : http://contextgarden.net
___________________________________________________________________________________

Re: question about MP drawing with dir

[Pablo Rodriguez]

On 05/24/2018 09:33 PM, Hans Hagen wrote:
> [...] 
> reusing a picture is more efficient
> 
> \startMPpage
>      draw fullcircle scaled (.06TextWidth - .05LineHeight);
>      picture t ; t := textext("\cldcontext{utf.char(0xEB09)}") ;
>      for m=1 step 2 until 10 :
>          path s ; s := (dir30--dir150--dir315--dir90--dir225--cycle) 
> scaled m;
>          n := (m * 50) ;
>          o := (m / 5) ;
>          for i=0 upto n :
>            draw t scaled (o * .025) shifted point (i/n*length s) of s ;
>          endfor
>      endfor
> \stopMPpage

Many thanks for the improvement, Hans.

Pablo
-- 
http://www.ousia.tk
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maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
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___________________________________________________________________________________

Re: question about MP drawing with dir

[Alan Braslau]

On Thu, 24 May 2018 21:01:59 +0200
Pablo Rodriguez <oinos@gmx.es> wrote:

> dir seems magic to me. I don’t understand how it works, not even how
> it can be used for drawing not having an origin.

All MP drawings have an origin (0,0).

(dir angle) returns a pair on a unit circle surrounding the origin, i.e.
(cosd angle,sind angle) where cosd is the cosine function operating on
an angle in degrees.

Alan
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___________________________________________________________________________________

Re: question about MP drawing with dir

[Pablo Rodriguez]

On 05/24/2018 10:23 PM, Alan Braslau wrote:
> On Thu, 24 May 2018 21:01:59 +0200
> Pablo Rodriguez <oinos@gmx.es> wrote:
> 
>> dir seems magic to me. I don’t understand how it works, not even how
>> it can be used for drawing not having an origin.
> 
> All MP drawings have an origin (0,0).

I thought origin had to be explicitly set.

> (dir angle) returns a pair on a unit circle surrounding the origin, i.e.
> (cosd angle,sind angle) where cosd is the cosine function operating on
> an angle in degrees.

Well, I need to refresh my math from high school (centuries ago :-)) to
remember what cosine and sine are.

Many thanks for your explanation,

Pablo
-- 
http://www.ousia.tk
___________________________________________________________________________________
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maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
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archive  : https://bitbucket.org/phg/context-mirror/commits/
wiki     : http://contextgarden.net
___________________________________________________________________________________