Re: Randomize control points in metapost/metafun?

["Mikael P. Sundqvist" <mickep@gmail.com>]

On Mon, Aug 1, 2016 at 10:12 AM, Hans Hagen <pragma@wxs.nl> wrote:
> On 8/1/2016 8:03 AM, Mikael P. Sundqvist wrote:
>>
>> Hi!
>>
>> I look for a way to randomize control points of a path, leaving the
>> coordinates themselves untouched.
>>
>> The reason is the following: I want to draw (for example) a circle
>> with a triangle inside, and I want them to look slightly randomized.
>> If I do (see attached pdf for a typical result of this)
>>
>> \startMPpage
>> draw fullcircle scaled 2cm randomized 0.1cm;
>> draw ((1cm,0)--(0,1cm)--(-1cm,0)--cycle) randomized 0.1cm;
>> \stopMPpage
>>
>> then the corners of the triangle does not stay on the circle (and I
>> want them to). [I dont want the triangle to consist of perfectly
>> straight lines, so I cannot (directly) draw the triangle using
>> different points along the randomized circle] I imagine that one could
>> achieve what I want if one could randomize the control points only.
>
>
> i'll add
>
> primarydef p randomizedcontrols s = (
>     if path p :
>         for i=0 upto length(p)-1 :
>              (point       i    of p) .. controls
>             ((postcontrol i    of p) randomshifted s) and
>             ((precontrol (i+1) of p) randomshifted s) ..
>         endfor
>         if cycle p :
>             cycle
>         else :
>             (point length(p) of p)
>         fi
>     else :
>         p randomized s
>     fi
> ) enddef ;
>
>> Also, is it possible to randomize a picture (consisting of several
>> paths/points) somehow, without randomizing each part of it manually?
>
>
> so:
>
> vardef mfun_randomized_path(expr p,s) =
>     for i=0 upto length(p)-1 :
>          (point       i    of p) .. controls
>         ((postcontrol i    of p) randomshifted s) and
>         ((precontrol (i+1) of p) randomshifted s) ..
>     endfor
>     if cycle p :
>         cycle
>     else :
>         (point length(p) of p)
>     fi
> enddef;
>
> vardef mfun_randomized_picture(expr p,s) =
>     save currentpicture ;
>     picture currentpicture ;
>     currentpicture := nullpicture ;
>     for i within p :
>         addto currentpicture
>             if stroked i :
>                 doublepath pathpart i randomizedcontrols s
>                 dashed dashpart i
>                 withpen penpart i
>                 withcolor colorpart i
>                 withprescript prescriptpart i
>                 withpostscript postscriptpart i
>             elseif filled i :
>                 contour pathpart i randomizedcontrols s
>                 withpen penpart i
>                 withcolor colorpart i
>                 withprescript prescriptpart i
>                 withpostscript postscriptpart i
>             else :
>                 also i
>             fi
>         ;
>     endfor ;
>     currentpicture
> enddef ;
>
> primarydef p randomizedcontrols s = (
>     if path p :
>         mfun_randomized_path(p,s)
>     elseif picture p :
>         mfun_randomized_picture(p,s)
>     else :
>         p randomized s
>     fi
> ) enddef ;
>
> with
>
> draw fullcircle scaled 2cm randomizedcontrols 0.1cm;
> draw ((1cm,0)--(0,1cm)--(-1cm,0)--cycle) randomizedcontrols 0.1cm;
>
> draw image (
>     draw fullcircle scaled 2cm ;
>     draw ((1cm,0)--(0,1cm)--(-1cm,0)--cycle);
> ) randomizedcontrols 0.1cm ;
>
>
>
> -----------------------------------------------------------------
>                                           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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Wow! That was fast! I just updated and it indeed works as expected.

I hate to ask another thing when I just got this fast and nice help,
but is there also a way to change the control points in such a way
that no _new_ sharp corners occur?

/Mikael
___________________________________________________________________________________
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://tex.aanhet.net
archive  : http://foundry.supelec.fr/projects/contextrev/
wiki     : http://contextgarden.net
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